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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2016	Feb. 22, 2017	Jun. 30, 2016
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Entity Registrant Name	AKAMAI TECHNOLOGIES INC
Entity Central Index Key	0001086222
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		173,190,922
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 9,531.0

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 324,169	$ 289,473
Marketable securities	512,849	460,088
Accounts receivable, net of reserves of $6,145 and $7,364 at December 31, 2016 and 2015, respectively	368,596	380,399
Prepaid expenses and other current assets	104,303	123,228
Total current assets	1,309,917	1,253,188
Property and equipment, net	801,017	753,180
Marketable securities	779,311	774,674
Goodwill	1,228,503	1,150,244
Acquired intangible assets, net	149,463	156,095
Deferred income tax assets	8,982	4,700
Other assets	95,953	89,603
Total assets	4,373,146	4,181,684
Current liabilities:
Accounts payable	76,120	61,982
Accrued expenses	238,777	216,166
Deferred revenue	52,972	54,154
Other current liabilities	6,719	138
Total current liabilities	374,588	332,440
Deferred revenue	3,758	4,163
Deferred income tax liabilities	11,652	12,888
Convertible senior notes	640,087	618,047
Other liabilities	118,691	93,268
Total liabilities	1,148,776	1,060,806
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock, $0.01 par value; 5,000,000 shares authorized; 700,000 shares designated as Series A Junior Participating Preferred Stock; no shares issued or outstanding	0	0
Common stock, $0.01 par value; 700,000,000 shares authorized; 173,254,797 and 177,212,181 shares issued and outstanding at December 31, 2016 and 2015, respectively	1,733	1,772
Additional paid-in capital	4,239,588	4,437,420
Accumulated other comprehensive loss	(56,222)	(41,453)
Accumulated deficit	(960,729)	(1,276,861)
Total stockholders’ equity	3,224,370	3,120,878
Total liabilities and stockholders’ equity	$ 4,373,146	$ 4,181,684

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable reserve (in dollars)	$ 6,145	$ 7,364
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares designated as Series A Junior Participating Preferred Stock	700,000	700,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	700,000,000	700,000,000
Common stock, shares issued	173,254,797	177,212,181
Common stock, shares outstanding	173,254,797	177,212,181

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 2,340,049	$ 2,197,448	$ 1,963,874
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	809,001	725,620	610,943
Research and development	167,628	148,591	125,286
Sales and marketing	426,967	440,988	379,035
General and administrative	439,916	388,265	325,845
Amortization of acquired intangible assets	26,642	27,067	32,057
Restructuring charges	10,301	767	1,189
Total costs and operating expenses	1,880,455	1,731,298	1,474,355
Income from operations	459,594	466,150	489,519
Interest income	14,702	11,200	7,680
Interest expense	(18,638)	(18,525)	(15,463)
Other income (expense), net	3,788	(2,201)	(1,960)
Income before provision for income taxes	459,446	456,624	479,776
Provision for income taxes	143,314	135,218	145,828
Net income	$ 316,132	$ 321,406	$ 333,948
Net income per share:
Basic (in dollars per share)	$ 1.81	$ 1.80	$ 1.87
Diluted (in dollars per share)	$ 1.79	$ 1.78	$ 1.84
Shares used in per share calculations:
Basic (in shares)	174,917	178,391	178,279
Diluted (in shares)	176,215	180,415	181,186

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 316,132	$ 321,406	$ 333,948
Other comprehensive loss:
Foreign currency translation adjustments	(14,081)	(22,872)	(15,349)
Change in unrealized loss on investments, net of income tax benefit of $432, $773 and $689 for the years ended December 31, 2016, 2015 and 2014, respectively	(688)	(970)	(171)
Other comprehensive loss	(14,769)	(23,842)	(15,520)
Comprehensive income	$ 301,363	$ 297,564	$ 318,428

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Tax expense (benefit) on change in unrealized gain (loss) on investments, net	$ (432)	$ (773)	$ (689)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 316,132	$ 321,406	$ 333,948
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	334,302	299,563	247,406
Stock-based compensation	144,506	126,677	111,996
Excess tax benefits from stock-based compensation	(5,514)	(29,301)	(32,238)
Provision (benefit) for deferred income taxes	7,308	4,098	(25,880)
Amortization of debt discount and issuance costs	18,638	18,525	15,463
Other non-cash reconciling items, net	10,574	5,804	2,565
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	3,356	(56,247)	(58,397)
Prepaid expenses and other current assets	23,881	7,137	(60,788)
Accounts payable and accrued expenses	18,491	51,624	94,698
Deferred revenue	(1,213)	3,224	7,725
Other current liabilities	5,484	(345)	(702)
Other non-current assets and liabilities	(9,647)	11,986	22,274
Net cash provided by operating activities	866,298	764,151	658,070
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(95,439)	(141,147)	(386,532)
Purchases of property and equipment	(180,949)	(311,676)	(207,159)
Capitalization of internal-use software development costs	(135,340)	(133,307)	(111,468)
Purchases of short- and long-term marketable securities	(781,061)	(692,879)	(1,225,409)
Proceeds from sales of short- and long-term marketable securities	57,740	2,008	373,730
Proceeds from maturities of short- and long-term marketable securities	664,837	843,931	372,287
Other non-current assets and liabilities	782	(2,494)	5,745
Net cash used in by investing activities	(469,430)	(435,564)	(1,178,806)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes, net of issuance costs	0	0	678,735
Proceeds from the issuance of warrants related to convertible senior notes	0	0	77,970
Purchase of note hedge related to convertible senior notes	0	0	(101,292)
Repayment of acquired debt and capital leases	0	0	(17,862)
Proceeds related to the issuance of common stock under stock plans	59,560	61,791	87,109
Excess tax benefits from stock-based compensation	5,514	29,301	32,238
Employee taxes paid related to net share settlement of stock-based awards	(45,545)	(54,164)	(50,649)
Repurchases of common stock	(373,794)	(302,606)	(268,647)
Other non-current assets and liabilities	0	(2,050)	(1,575)
Net cash provided by (used in) financing activities	(354,265)	(267,728)	436,027
Effects of exchange rate changes on cash and cash equivalents	(7,907)	(10,036)	(10,532)
Net increase (decrease) in cash and cash equivalents	34,696	50,823	(95,241)
Cash and cash equivalents at beginning of year	289,473	238,650	333,891
Cash and cash equivalents at end of year	324,169	289,473	238,650
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received in the years ended December 31, 2016 and 2015 of $1,664 and $19,374, respectively	120,223	75,033	166,211
Non-cash financing and investing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	36,742	19,327	45,868
Capitalization of stock-based compensation	$ 23,093	$ 17,867	$ 15,226

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Income tax refund received	$ 1,664	$ 19,374

Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2013		178,580,696
Balance as of January 1, 2016 at Dec. 31, 2013	$ 2,629,431	$ 1,808	$ 4,561,929	$ 0	$ (2,091)	$ (1,932,215)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		3,648,994
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	6,458	$ 14	6,444
Issuance of common stock under employee stock purchase plan (in shares)		700,879
Issuance of common stock under employee stock purchase plan	29,271	$ 7	29,264
Stock-based compensation	127,222		127,222
Tax benefits from stock-based award activity, net	26,867		26,867
Equity component of convertible senior notes, net of issuance costs of $1,649	99,627		99,627
Issuance costs of convertible senior notes	1,649
Issuance of warrants related to convertible senior notes	77,970		77,970
Purchase of note hedge related to convertible senior notes	(101,292)		(101,292)
Repurchases of common stock (in shares)		(4,629,966)
Repurchases of common stock	(268,647)			(268,647)
Treasury stock retirement	0	$ (46)	(268,601)	268,647
Net income	333,948					333,948
Foreign currency translation adjustments	(15,349)				(15,349)
Change in unrealized gain on investments, net of tax	(171)				(171)
Ending balance (in shares) at Dec. 31, 2014		178,300,603
Balance as of December 31, 2016 at Dec. 31, 2014	2,945,335	$ 1,783	4,559,430	0	(17,611)	(1,598,267)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		2,756,357
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	(27,670)	$ 27	(27,697)
Issuance of common stock under employee stock purchase plan (in shares)		668,654
Issuance of common stock under employee stock purchase plan	34,841	$ 7	34,834
Stock-based compensation	144,544		144,544
Tax benefits from stock-based award activity, net	28,870		28,870
Repurchases of common stock (in shares)		(4,513,433)
Repurchases of common stock	(302,606)			(302,606)
Treasury stock retirement	0	$ (45)	(302,561)	302,606
Net income	321,406					321,406
Foreign currency translation adjustments	(22,872)				(22,872)
Change in unrealized gain on investments, net of tax	(970)				(970)
Ending balance (in shares) at Dec. 31, 2015		177,212,181
Balance as of December 31, 2016 at Dec. 31, 2015	3,120,878	$ 1,772	4,437,420	0	(41,453)	(1,276,861)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		2,194,699
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	(27,394)	$ 22	(27,416)
Issuance of common stock under employee stock purchase plan (in shares)		863,419
Issuance of common stock under employee stock purchase plan	39,914	$ 9	39,905
Stock-based compensation	166,987		166,987
Tax deficiency from stock-based award activity, net	(3,584)		(3,584)
Repurchases of common stock (in shares)		(7,015,502)
Repurchases of common stock	(373,794)			(373,794)
Treasury stock retirement	0	$ (70)	(373,724)	373,794
Net income	316,132					316,132
Foreign currency translation adjustments	(14,081)				(14,081)
Change in unrealized gain on investments, net of tax	(688)				(688)
Ending balance (in shares) at Dec. 31, 2016		173,254,797
Balance as of December 31, 2016 at Dec. 31, 2016	$ 3,224,370	$ 1,733	$ 4,239,588	$ 0	$ (56,222)	$ (960,729)

Nature of Business and Basis of Presentation	12 Months Ended
Nature of Business and Basis of Presentation	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Nature of Business and Basis of Presentation Akamai Technologies, Inc. (the “Company”) provides cloud services for delivering, optimizing and securing content and business applications. The Company's globally-distributed platform comprises more than 200,000 servers in over 1,600 networks in 131 countries. The Company was incorporated in Delaware in 1998 and is headquartered in Cambridge, Massachusetts. The Company currently operates in one industry segment: providing cloud services for delivering, optimizing and securing content and business applications over the Internet. The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in the accompanying consolidated financial statements.

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2016
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The Company prepares its consolidated financial statements in conformity with accounting principles generally accepted in the United States of America. These principles require management to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the amounts disclosed in the related notes to the consolidated financial statements. Actual results and outcomes may differ materially from management’s estimates, judgments and assumptions. Significant estimates, judgments and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, valuation and impairment of investments and marketable securities, valuation and useful lives of acquired intangible assets, useful lives and realizability of long-lived assets, capitalized internal-use software development costs, income tax reserves and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. The effects of material revisions in estimates are reflected in the consolidated financial statements prospectively from the date of the change in estimate. Cash, Cash Equivalents and Marketable Securities Cash and cash equivalents consist of cash held in bank deposit accounts and short-term, highly-liquid investments with remaining maturities of three months or less at the date of purchase. Marketable securities consist of corporate, government and other securities. Securities having remaining maturities of less than one year from the date of the balance sheet are classified as short-term, and those with maturities of more than one year from the date of the balance sheet are classified as long-term in the consolidated balance sheet. The Company classifies its debt and equity investments with readily determinable market values as available-for-sale. These investments are classified as marketable securities on the consolidated balance sheets and are carried at fair market value, with unrealized gains and losses considered to be temporary in nature and reported as accumulated other comprehensive loss, a separate component of stockholders’ equity. The Company reviews all investments for reductions in fair value that are other-than-temporary. When such reductions occur, the cost of the investment is adjusted to fair value through recording a loss on investments in the consolidated statements of income. Gains and losses on investments are calculated on the basis of specific identification. Marketable securities are considered to be impaired when a decline in fair value below cost basis is determined to be other-than-temporary. The Company periodically evaluates whether a decline in fair value below cost basis is other-than-temporary by considering available evidence regarding these investments including, among other factors: the duration of the period that, and extent to which, the fair value is less than cost basis; the financial health and business outlook of the issuer, including industry and sector performance and operational and financing cash flow factors; overall market conditions and trends and the Company’s intent and ability to retain its investment in the security for a period of time sufficient to allow for an anticipated recovery in market value. Once a decline in fair value is determined to be other-than-temporary, a write-down is recorded and a new cost basis in the security is established. Assessing the above factors involves inherent uncertainty. Write-downs, if recorded, could be materially different from the actual market performance of marketable securities in the Company’s portfolio if, among other things, relevant information related to the marketable securities was not publicly available or other factors not considered by the Company would have been relevant to the determination of impairment. Accounts Receivable and Related Reserves The Company’s accounts receivable balance includes unbilled amounts that represent revenue recorded for customers that are typically billed monthly in arrears. The Company records reserves against its accounts receivable balance. These reserves consist of allowances for doubtful accounts and reserves for cash-basis customers. Increases and decreases in the allowance for doubtful accounts are included as a component of general and administrative expense in the consolidated statements of income. The Company’s reserve for cash-basis customers increases as services are provided to customers where collection is no longer assured. Increases to the reserve for cash-basis customers are recorded as reductions of revenue. The reserve decreases and revenue is recognized when and if cash payments are received. Estimates are used in determining these reserves and are based upon the Company’s review of outstanding balances on a customer-specific, account-by-account basis. The allowance for doubtful accounts is based upon a review of customer receivables from prior sales with collection issues where the Company no longer believes that the customer has the ability to pay for services previously provided. The Company also performs ongoing credit evaluations of its customers. If such an evaluation indicates that payment is no longer reasonably assured for services provided, any future services provided to that customer will result in the creation of a cash-basis reserve until the Company receives consistent payments. The Company does not have any off-balance sheet credit exposure related to its customers. Concentrations of Credit Risk The amounts reflected in the consolidated balance sheets for accounts receivable, other current assets, accounts payable, accrued liabilities and other current liabilities approximate their fair values due to their short-term maturities. The Company maintains the majority of its cash, cash equivalents and marketable securities with major financial institutions that the Company believes to be of high credit standing. The Company believes that, as of December 31, 2016, its concentration of credit risk related to cash equivalents and marketable securities was not significant. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which the Company makes substantial sales. The Company’s customer base consists of a large number of geographically-dispersed customers diversified across several industries. To reduce risk, the Company routinely assesses the financial strength of its customers. Based on such assessments, the Company believes that its accounts receivable credit risk exposure is limited. For the years ended December 31, 2016, 2015 and 2014, no customer accounted for more than 10% of total revenue. As of December 31, 2016, 2015 and 2014, no customer had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2016, its concentration of credit risk related to accounts receivable was not significant. Fair Value of Financial Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company has certain financial assets and liabilities recorded at fair value, principally cash equivalents and short- and long-term marketable securities that have been classified as Level 1, 2 or 3 within the fair value hierarchy. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the reporting date. Fair values determined by Level 2 inputs utilize data points other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Fair values determined by Level 3 inputs are based on unobservable data points for the asset or liability. Property and Equipment Property and equipment are recorded at cost, net of accumulated depreciation and amortization. Property and equipment generally include purchases of items with a per-unit value greater than $1,000 and an estimated useful life greater than one year. Depreciation and amortization are computed on a straight-line basis over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the related lease terms or their estimated useful lives. The Company periodically reviews the estimated useful lives of property and equipment, and any changes to the estimated useful lives are recorded prospectively from the date of the change. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are removed from the accounts, and any resulting gain or loss is included in income from operations. Repairs and maintenance costs are expensed as incurred. Goodwill, Acquired Intangible Assets and Long-Lived Assets Goodwill is the amount by which the cost of acquired net assets in a business combination exceeds the fair value of the net identifiable assets on the date of purchase and is carried at its historical cost. The Company tests goodwill for impairment on an annual basis or more frequently if events or changes in circumstances indicate that the asset might be impaired. The Company performs its impairment test of goodwill as of December 31. As of December 31, 2016, 2015 and 2014, the fair value of the Company's reporting unit was substantially in excess of the carrying value. The tests did not result in an impairment to goodwill during the years ended December 31, 2016, 2015 and 2014. Acquired intangible assets consist of completed technologies, customer relationships, trademarks and trade names, non-compete agreements and acquired license rights. Acquired intangible assets, other than goodwill, are amortized over their estimated useful lives based upon the estimated economic value derived from the related intangible asset. Long-lived assets, including property and equipment and acquired intangible assets, are reviewed for impairment whenever events or changes in circumstances, such as service discontinuance, technological obsolescence, significant decreases in the Company’s market capitalization, facility closures or work-force reductions indicate that the carrying amount of the long-lived asset may not be recoverable. When such events occur, the Company compares the carrying amount of the asset to the undiscounted expected future cash flows related to the asset. If this comparison indicates that an impairment is present, the amount of the impairment is calculated as the difference between the carrying amount and the fair value of the asset. Revenue Recognition The Company recognizes service revenue in accordance with the authoritative guidance for revenue recognition, including guidance on revenue arrangements with multiple deliverables. Revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, the service is performed and collectability of the resulting receivable is reasonably assured. The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. These contracts generally commit the customer to a minimum of monthly, quarterly or annual level of usage and specify the rate at which the customer must pay for actual usage above the monthly, quarterly or annual minimum. For contracts with a monthly commitment, the Company recognizes the monthly minimum as revenue each month, provided that an enforceable contract has been signed by both parties, the service has been delivered to the customer, the fee for the service is fixed or determinable and collection is reasonably assured. Should a customer’s usage of the Company's services exceed the monthly, quarterly or annual minimum, the Company recognizes revenue for such excess in the period of additional usage. For annual or other non-monthly period revenue commitments, the Company recognizes revenue monthly based upon the customer’s actual usage each month of the commitment period and only recognizes any remaining committed amount for the applicable period in the last month thereof. The Company typically charges its customers an integration fee when the services are first activated. Integration fees are recorded as deferred revenue and recognized as revenue ratably over the estimated life of the customer arrangement. The Company also derives revenue from services sold as discrete, non-recurring events or based solely on usage. For these services, the Company recognizes revenue once the event or usage has occurred. When more than one element is contained in a revenue arrangement, the Company determines the fair value for each element in the arrangement based on vendor-specific objective evidence (“VSOE”) for each respective element, including any renewal rates for services contractually offered to the customer. Elements typically included in the Company's multiple element arrangements consist of its core services – the delivery of content, applications and software over the Internet – as well as mobile and security solutions and enterprise professional services. These elements have value to the customer on a stand-alone basis in that they can be sold separately by another vendor. Generally, there is no right of return relative to these services. The Company typically uses VSOE to determine the fair value of its separate elements. All stand-alone sales of professional services are reviewed to establish the average stand-alone selling price for those services. For the Company's core services, the fair value is the price charged for a single deliverable on a per unit basis when it is sold separately. For arrangements in which the Company is unable to establish VSOE, third party evidence ("TPE") of the fair value of each element is determined based upon the price charged when the element is sold separately by another vendor. For arrangements in which the Company is unable to establish VSOE or TPE for each element, the Company uses the best estimate of selling price ("BESP") to determine the fair value of the separate deliverables. The Company estimates BESP based upon a management-approved listing of unit pricing for all solutions and pre-established discount levels for each solution that takes into consideration volume, geography and industry lines. The Company allocates arrangement consideration across the multiple elements using the relative selling price method. At the inception of a customer contract, the Company makes an assessment as to that customer’s ability to pay for the services provided. The Company bases its assessment on a combination of factors, including the successful completion of a credit check or financial review, its collection experience with the customer and other forms of payment assurance. Upon the completion of these steps, the Company recognizes revenue monthly in accordance with its revenue recognition policy. If the Company subsequently determines that collection from the customer is not reasonably assured, the Company records an allowance for doubtful accounts and bad debt expense for all of that customer’s unpaid invoices and ceases recognizing revenue for continued services provided until cash is received from the customer. Changes in the Company’s estimates and judgments about whether collection is reasonably assured would change the timing of revenue or amount of bad debt expense that the Company recognizes. The Company also sells its services through reseller channels. Assuming all other revenue recognition criteria are met, the Company recognizes revenue from reseller arrangements based on the reseller’s contracted non-refundable minimum purchase commitments over the term of the contract, plus amounts sold by the reseller to its customers in excess of the minimum commitments. Amounts attributable to this excess usage are recognized as revenue in the period in which the service is provided. From time to time, the Company enters into contracts to sell its services or license its technology to unrelated enterprises at or about the same time that it enters into contracts to purchase products or services from the same enterprises. If the Company concludes that these contracts were negotiated concurrently, the Company records as revenue only the net cash received from the vendor, unless the product or service received has a separate identifiable benefit and the fair value of the vendor’s product or service can be established objectively. The Company may from time to time resell licenses or services of third parties. The Company records revenue for these transactions on a gross basis when the Company has risk of loss related to the amounts purchased from the third party and the Company adds value to the license or service, such as by providing maintenance or support for such license or service. If these conditions are present, the Company recognizes revenue when all other revenue recognition criteria are satisfied. Deferred revenue represents amounts billed to customers for which revenue has not been recognized. Deferred revenue primarily consists of the unearned portion of monthly billed service fees, prepayments made by customers for future periods, deferred integration and activation set-up fees and amounts billed under customer arrangements with extended payment terms. Cost of Revenue Cost of revenue consists primarily of fees paid to network providers for bandwidth and to third party network data centers for housing servers, also known as co-location costs. Cost of revenue also includes employee costs for services delivery and network operation, build-out and support of the Company's network; network storage costs; cost of software licenses; depreciation of network equipment used to deliver the Company’s services; amortization of network-related internal-use software; and costs for the production of live events. The Company enters into contracts for bandwidth with third party network providers with terms typically ranging from several months to five years. These contracts generally commit the Company to pay minimum monthly fees plus additional fees for bandwidth usage above the committed level. In some circumstances, Internet service providers (“ISPs”) make rack space available for the Company’s servers and access to their bandwidth at a discount or no cost. In exchange, the ISP and its customers benefit by receiving content through a local Company server resulting in better content delivery. The Company does not consider these relationships to represent the culmination of an earnings process. Accordingly, the Company does not recognize as revenue the value to the ISPs associated with the use of the Company’s servers, nor does the Company recognize as expense the value of the rack space and bandwidth received at discounted or no cost. Research and Development Costs and Capitalized Internal-Use Software Research and development costs consist primarily of payroll and related personnel costs for the design, development, deployment, testing and enhancement of the Company’s services and network. Costs incurred in the development of the Company’s services are expensed as incurred, except certain internal-use software development costs eligible for capitalization. Capitalized costs include external consulting fees, payroll and payroll-related costs and stock-based compensation for employees in the Company’s development and information technology groups who are directly associated with, and who devote time to, the Company’s internal-use software projects. Capitalization begins when the planning stage is complete and the Company commits resources to the software project, and continues during the application development stage. Capitalization ceases when the software has been tested and is ready for its intended use. Costs incurred during the planning, training and post-implementation stages of the software development life-cycle are expensed as incurred. The Company amortizes completed internal-use software that is used on its network to cost of revenue over its estimated useful life. Accounting for Stock-Based Compensation The Company recognizes compensation costs for all stock-based payment awards made to employees based upon the awards’ grant-date fair value. The stock-based payment awards include stock options, restricted stock units, deferred stock units and employee stock purchases related to the Company’s employee stock purchase plan. For stock options, the Company has selected the Black-Scholes option-pricing model to determine the fair value of stock option awards. For stock awards with market-based vesting conditions, the Company uses a Monte Carlo simulation to determine the fair value of the award. For stock options, restricted stock units and deferred stock units that contain only a service-based vesting feature, the Company recognizes compensation cost on a straight-line basis over the award's vesting period. For awards with a performance condition-based vesting feature, the Company recognizes compensation cost on a graded-vesting basis over the award's expected vesting period, commencing when achievement of the performance condition is deemed probable. In addition, for awards that vest and become exercisable only upon achievement of specified performance conditions, the Company makes judgments and estimates each quarter about the probability that such performance conditions will be met or achieved. Any changes to those estimates that the Company makes from time to time may have a significant impact on the stock-based compensation expense recorded and could materially impact the Company’s results of operations. Foreign Currency Translation and Forward Currency Contracts The assets and liabilities of the Company's subsidiaries are translated at the applicable exchange rate as of the balance sheet date, and revenue and expenses are translated at an average rate over the period. Resulting currency translation adjustments are recorded as a component of accumulated other comprehensive loss, a separate component of stockholders’ equity. Gains and losses on inter-company and other non-functional currency transactions are recorded in other income (expense), net. The Company enters into short-term foreign currency forward contracts to offset foreign exchange gains and losses generated by the re-measurement of certain assets and liabilities recorded in non-functional currencies. Changes in the fair value of these derivatives, as well as re-measurement gains and losses, are recognized in current earnings in other income (expense), net. As of December 31, 2016 and 2015, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2016, 2015 and 2014 were immaterial. The Company's foreign currency forward contracts may be exposed to credit risk to the extent that its counterparties are unable to meet the terms of the agreements. The Company seeks to minimize counterparty credit (or repayment) risk by entering into transactions only with major financial institutions of investment grade credit rating. Taxes The Company's provision for income taxes is comprised of a current and a deferred portion. The current income tax provision is calculated as the estimated taxes payable or refundable on tax returns for the current year. The deferred income tax provision is calculated as the estimated future tax effects attributable to temporary differences and carryforwards using expected tax rates in effect during the years in which the differences are expected to reverse or the carryforwards are expected to be realized. The Company currently has net deferred tax assets consisting of net operating loss (“NOL”) carryforwards, tax credit carryforwards and deductible temporary differences. Management periodically weighs the positive and negative evidence to determine if it is more likely than not that some or all of the deferred tax assets will be realized. The Company has recorded certain tax reserves to address potential exposures involving its income tax and sales and use tax positions. These potential tax liabilities result from the varying application of statutes, rules, regulations and interpretations by different taxing jurisdictions. The Company's estimate of the value of its tax reserves contains assumptions based on past experiences and judgments about the interpretation of statutes, rules and regulations by taxing jurisdictions. It is possible that the costs of the ultimate tax liability or benefit from these matters may be more or less than the amount the Company estimated. Uncertainty in income taxes is recognized in the Company's consolidated financial statements using a two-step process. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The Company has elected to account for the indirect income tax effects of stock-based compensation as provision for income taxes. This primarily includes the impact of the research and development tax credit and the domestic production activities deduction. Newly-Adopted Accounting Pronouncements In April 2015, the Financial Accounting Standards Board (“FASB”) issued updated guidance to simplify the presentation of debt issuance costs on the balance sheets. This guidance moved debt issuance costs from the assets section of the balance sheet to the liabilities section as a direct deduction from the carrying amount of the debt issued. The Company retrospectively adopted the guidance on January 1, 2016. The prior period consolidated balance sheet presented, as of December 31, 2015, was revised to reclassify $6.2 million of debt issuance costs included in other assets to convertible senior notes. This had the impact of reducing the Company's total assets and total liabilities by $6.2 million, as of December 31, 2015. This reclassification did not have a material impact on the Company's consolidated financial statements. In September 2015, the FASB issued updated guidance that eliminates the requirement that an acquirer in a business combination account for measurement period adjustments retrospectively. In an effort to reduce complexity in financial reporting, the new guidance requires that the cumulative impact of a measurement period adjustment, including the impact on prior periods, be recognized in the reporting period in which the adjustment is identified. The standard was effective for and adopted by the Company on January 1, 2016. This guidance did not have an impact on the Company's consolidated financial statements as the measurement periods for the Company's 2015 acquisitions were closed as of December 31, 2015. Recent Accounting Pronouncements In May 2014, the FASB issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step model for recognizing revenue from contracts with customers. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard can be adopted using one of two methods: retrospectively to each prior period presented or a modified retrospective application by recognizing a cumulative-effect adjustment as a component of equity as of the date of adoption. The updated guidance modifies certain judgments and estimates that the Company currently makes as it relates to recognizing revenue. Upon adoption of the new revenue standard, integration fee revenue that was previously recognized ratably over the estimated life of the customer arrangement will be recognized when integration has been completed, which will have the effect of accelerating revenue from integration fees. In addition, the Company currently establishes a reserve for cash basis customers if collectability is not reasonably assured and recognizes revenue as cash is collected. Upon adoption of the new standard, revenue will be recognized for those customers when collectability becomes probable, rather than as cash is collected. The Company is also assessing the impact of capitalizing costs associated with obtaining customer contracts, specifically commission and incentive payments. Currently, these payments are expensed in the period they are incurred. Under the updated guidance, these payments will be deferred on the Company's consolidated balance sheets and amortized over the expected life of the customer contract. This standard will be effective for the Company on January 1, 2018. The Company continues to evaluate the potential impact of adopting this new accounting guidance on its consolidated financial statements. In February 2016, the FASB issued guidance that requires companies to present assets and liabilities arising from leases with a term greater than 12 months on the consolidated balance sheets. The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize right-of-use assets and lease liabilities on the balance sheet and requiring disclosure of key information about leasing arrangements. This will impact all leases, which include leases for real estate and co-location facilities, among other arrangements currently under evaluation. The Company plans to adopt this standard in the first quarter of 2019 and expects to record significant right-of-use assets and lease liabilities on its consolidated balance sheets. In March 2016, the FASB issued guidance that is intended to simplify aspects of how share-based payments are accounted for and presented in financial statements. This guidance requires that entities record all tax effects of share-based payments at settlement or expiration through the income statement. The standard also amends how windfall tax benefits are recognized, the minimum statutory tax withholding requirements and how entities elect to recognize share-based payment forfeitures. In addition, this guidance impacts the presentation of cash flows related to excess tax benefits by no longer requiring separate presentation as a financing activity apart from other operating income tax cash flows. This guidance was effective for the Company beginning on January 1, 2017. Upon adoption on a prospective basis, the Company is recognizing excess tax benefits in its provision for income taxes rather than as additional paid-in capital. In addition, the Company expects to adopt the presentation requirements related to the excess tax benefit in its cash flows on a retrospective basis, which will result in an increase to cash flows from operating activities of $5.5 million and $29.3 million with a corresponding decrease to cash flows from financing activities for the years ended December 31, 2016 and 2015, respectively. Finally, the Company expects to continue estimating forfeitures in determining the amount of compensation cost. In June 2016, the FASB issued guidance that introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new "expected loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. This guidance will be effective for the Company on January 1, 2020. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements. In October 2016, the FASB issued guidance that requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. This guidance will be effective for the Company on January 1, 2018 and is to be applied on a modified retrospective basis through a recognizing cumulative-effect adjustment as a component of equity as of the date of adoption. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements.

Fair Value Measurements

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

The following is a summary of available-for-sale marketable securities held as of December 31, 2016 and 2015 (in thousands):



			Gross Unrealized					Aggregate Fair Value		Classification on Balance Sheet
	Amortized Cost									Short-Term Marketable Securities		Long-Term Marketable Securities
As of December 31, 2016	Amortized Cost		Gains		Losses					Short-Term Marketable Securities		Long-Term Marketable Securities
Commercial paper	$	40,965	$	—	$	(45	)	$	40,920	$	40,920	$	—
Corporate bonds	984,650		123		(3,697		)	981,076		418,495		562,581
U.S. government agency obligations	267,473		35		(1,366		)	266,142		53,157		212,985
	$	1,293,088	$	158	$	(5,108	)	$	1,288,138	$	512,572	$	775,566

As of December 31, 2015
Commercial paper	$	2,491	$	—	$	(4	)	$	2,487	$	2,487	$	—
Corporate bonds	995,100		73		(3,365		)	991,808		432,585		559,223
U.S. government agency obligations	239,587		41		(575		)	239,053		25,016		214,037
	$	1,237,178	$	114	$	(3,944	)	$	1,233,348	$	460,088	$	773,260

The Company offers certain eligible employees the ability to participate in a non-qualified deferred compensation

plan. The mutual funds held by the Company that are associated with this plan are classified as restricted trading securities.

These securities are not included in the available-for-sale securities table above but are included in marketable securities in the

consolidated balance sheets.

Unrealized gains and unrealized temporary losses on investments classified as available-for-sale are included within accumulated other comprehensive loss in the consolidated balance sheets. Upon realization, those amounts are reclassified from accumulated other comprehensive loss to interest income in the consolidated statements of income. As of December 31, 2016, the Company held for investment corporate bonds with a fair value of $13.8 million, which are classified as available-for-sale marketable securities and have been in a continuous unrealized loss position for more than 12 months. The unrealized losses are not significant and are attributable to changes in interest rates. The Company does not believe any unrealized losses represent other than temporary impairments based on the evaluation of available evidence.

The following table details the fair value measurements within the fair value hierarchy of the Company’s financial assets and liabilities as of December 31, 2016 and 2015 (in thousands):



	Total Fair Value			Fair Value Measurements at Reporting Date Using
	Total Fair Value			Level 1		Level 2		Level 3
As of December 31, 2016
Cash Equivalents and Marketable Securities:
Money market funds	$	8,726		$	8,726	$	—	$	—
Commercial paper	40,920			—		40,920		—
Corporate bonds	981,076			—		981,076		—
U.S. government agency obligations	266,142			—		266,142		—
Mutual funds	4,022			4,022		—		—
	$	1,300,886		$	12,748	$	1,288,138	$	—

Liabilities:
Contingent consideration obligation related to completed acquisitions	$	(7,100	)	$	—	$	—	$	(7,100	)

As of December 31, 2015
Cash Equivalents and Marketable Securities:
Money market funds	$	1,250		$	1,250	$	—	$	—
Commercial paper	2,487			—		2,487		—
Corporate bonds	991,808			—		991,808		—
U.S. government agency obligations	239,053			—		239,053		—
Mutual funds	1,414			1,414		—		—
	$	1,236,012		$	2,664	$	1,233,348	$	—

The following table reflects the activity for the Company’s major classes of liabilities measured at fair value using Level 3 inputs for the years ended December 31, 2016 and 2015 (in thousands):



	Other Liabilities: Contingent Consideration Obligation
Balance, January 1, 2015	$	(900	)
Fair value adjustment to Velocius contingent consideration included in general and administrative expense	(100		)
Achievement of final milestone related to Velocius contingent consideration	1,000
Balance, December 31, 2015	$	—
Contingent consideration obligation related to Soha Systems, Inc. acquisition	(1,600		)
Contingent consideration obligation related to Cyberfend, Inc. acquisition	(5,500		)
Balance, December 31, 2016	$	(7,100	)

As of December 31, 2016 and 2015, the Company grouped money market funds and mutual funds using a Level 1 valuation because market prices for such investments are readily available in active markets. As of December 31, 2016 and 2015, the Company grouped commercial paper, U.S. government agency obligations and corporate bonds using a Level 2 valuation because quoted prices for identical or similar assets are available in markets that are inactive. The Company did not have any transfers of assets or liabilities between Level 1 and Level 2 of the fair value measurement hierarchy during the years ended December 31, 2016 and 2015.

When developing fair value estimates, the Company maximizes the use of observable inputs and minimizes the use of unobservable inputs. When available, the Company uses quoted market prices to measure fair value. The valuation technique used to measure fair value for the Company's Level 1 and Level 2 assets is a market approach, using prices and other relevant information generated by market transactions involving identical or comparable assets. If market prices are not available, the fair value measurement is based on models that use primarily market-based parameters including yield curves, volatilities, credit ratings and currency rates. In certain cases where market rate assumptions are not available, the Company is required to make judgments about assumptions market participants would use to estimate the fair value of a financial instrument.

The valuation technique used to measure fair value of the Company's Level 3 liabilities, which consists of contingent consideration related to the acquisitions of Soha Systems, Inc. ("Soha") and Cyberfend, Inc. ("Cyberfend") in 2016 (Note 8), was primarily an income approach. The significant unobservable input used in the fair value measurement of the contingent consideration is the likelihood of achieving development milestones to integrate the acquired technology into the Company's technology as well as achieving certain post-closing financial results.

Contractual maturities of the Company’s available-for-sale marketable securities held as of December 31, 2016 and 2015 were as follows (in thousands):



	December 31, 2016		December 31, 2015
Due in 1 year or less	$	512,572	$	460,088
Due after 1 year through 5 years	775,566		773,260
	$	1,288,138	$	1,233,348

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Accounts Receivable

12 Months Ended

Dec. 31, 2016

Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]

Accounts Receivable

Net accounts receivable consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016			December 31, 2015
Trade accounts receivable	$	260,976		$	262,885
Unbilled accounts receivable	113,765			124,878
Gross accounts receivable	374,741			387,763
Allowance for doubtful accounts	(829		)	(906		)
Reserve for cash-basis customers	(5,316		)	(6,458		)
Total accounts receivable reserves	(6,145		)	(7,364		)
Accounts receivable, net	$	368,596		$	380,399

A summary of activity in the accounts receivable reserves for the years ended December 31, 2016, 2015 and 2014, is as follows (in thousands):



	2016			2015			2014
Beginning balance	$	7,364		$	9,023		$	3,703
Charges to income from operations	49,677			37,870			32,293
Collections from cash basis customers and write-offs	(50,896		)	(39,529		)	(26,973		)
Ending balance	$	6,145		$	7,364		$	9,023

Charges to income from operations represent charges to bad debt expense for increases in the allowance for doubtful accounts and reductions to revenue for increases in reserves for cash basis customers.

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2016

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016		December 31, 2015
Prepaid income taxes	$	25,161	$	31,045
Other prepaid expenses	40,532		43,751
Other current assets	38,610		48,432
Total	$	104,303	$	123,228

Property and Equipment

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and equipment consisted of the following as of December 31, 2016 and 2015 (dollars in thousands):



	December 31, 2016			December 31, 2015			Estimated Useful Life in Years
Computer and networking equipment	$	1,170,471		$	1,046,739		3-7
Purchased software	51,727			46,509			3-10
Furniture and fixtures	41,968			35,212			5
Office equipment	24,497			21,108			3-5
Leasehold improvements	139,991			119,466			1-16
Internal-use software	656,053			546,520			2-7
Property and equipment, gross	2,084,707			1,815,554
Accumulated depreciation and amortization	(1,283,690		)	(1,062,374		)
Property and equipment, net	$	801,017		$	753,180

Depreciation and amortization expense on property and equipment and capitalized internal-use software for the years ended December 31, 2016, 2015 and 2014 was $307.7 million, $272.5 million and $215.3 million, respectively. During the years ended December 31, 2016, 2015 and 2014, the Company capitalized $23.1 million, $17.9 million and $15.2 million, respectively, of stock-based compensation related to employees who developed and enhanced internal-use software applications.

During the years ended December 31, 2016 and 2015, the Company wrote off $93.4 million and $48.7 million, respectively, of property and equipment, gross, along with the associated accumulated depreciation and amortization. The write-offs were primarily related to computer and networking equipment and internal-use software no longer in use. These assets had been substantially depreciated and amortized.

Goodwill and Acquired Intangible Assets

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Acquired Intangible Assets

The changes in the carrying amount of goodwill for the years ended December 31, 2016 and 2015 were as follows (in thousands):



	2016			2015
Beginning balance	$	1,150,244		$	1,051,294
Acquisition of Xerocole, Inc.	—			12,859
Acquisition of Codemate A/S	—			69,445
Acquisition of Bloxx Limited	—			17,694
Acquisition of Concord Systems, Inc.	1,079			—
Acquisition of Soha Systems, Inc.	43,515			—
Acquisition of Cyberfend, Inc.	38,754			—
Foreign currency translation	(5,089		)	(1,048		)
Ending balance	$	1,228,503		$	1,150,244

Acquired intangible assets that are subject to amortization consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016							December 31, 2015
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Completed technologies	$	119,091	$	(50,823	)	$	68,268	$	120,791	$	(58,633	)	$	62,158
Customer-related intangible assets	192,810		(114,209		)	78,601		191,710		(102,872		)	88,838
Non-compete agreements	5,030		(3,775		)	1,255		6,540		(3,374		)	3,166
Trademarks and trade names	3,700		(2,361		)	1,339		3,700		(1,767		)	1,933
Acquired license rights	490		(490		)	—		490		(490		)	—
Total	$	321,121	$	(171,658	)	$	149,463	$	323,231	$	(167,136	)	$	156,095

Aggregate expense related to amortization of acquired intangible assets for the years ended December 31, 2016, 2015 and 2014 was $26.6 million, $27.1 million and $32.1 million, respectively. Based on the Company's acquired intangible assets as of December 31, 2016, aggregate expense related to amortization of acquired intangible assets is expected to be approximately $29.2 million, $26.4 million, $25.0 million, $21.1 million and $16.6 million for the years ending December 31, 2017, 2018, 2019, 2020 and 2021, respectively.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Business Acquisitions and Divestitures

12 Months Ended

Dec. 31, 2016

Business Combinations [Abstract]

Business Acquisitions and Divestitures

Acquisition-related costs were $1.7 million, $1.8 million and $4.2 million during the years ended December 31, 2016, 2015 and 2014, respectively, and are included in general and administrative expense in the consolidated statements of income. Pro forma results of operations for the acquisitions completed in the years ended December 31, 2016, 2015 and 2014 have not been presented because the effects of the acquisitions, individually and in the aggregate, are not material to the Company's consolidated financial results. Revenue and earnings attributable to acquired operations since the dates of their acquisitions are included in the Company's consolidated statements of income and not presented separately because they are not material.

2016 Acquisitions

Concord Systems

On September 23, 2016, the Company acquired Concord Systems, Inc. ("Concord"), a provider of technology for processing data at scale, for $3.0 million in cash. The acquisition is expected to provide the Company with technology to complement existing platform data processing capabilities. The Company allocated $1.1 million of the cost of the acquisition to goodwill and $2.8 million to an identifiable intangible asset with a useful life of 7.0 years. The value of the goodwill is primarily attributable to synergies related to the integration of Concord technology onto the Company's platform as well as a trained technical workforce. An insignificant portion of the goodwill related to the acquisition of Concord is expected to be deducted for tax purposes. The allocation of the purchase price was finalized in the fourth quarter of 2016.

Soha Systems

On October 3, 2016, the Company acquired Soha, a provider of technology designed to facilitate secure access to enterprise applications, for $55.0 million in initial consideration and up to an additional $5.0 million for the achievement of post-closing milestones. The acquisition is intended to complement the Company's strategy of securing, protecting and accelerating enterprise applications and services in the cloud. The Company allocated $43.5 million of the cost of the acquisition to goodwill and $10.7 million to identifiable intangible assets. The total weighted average useful life of the intangible assets acquired from Soha is 4.7 years. The value of the goodwill is primarily attributable to synergies related to the integration of Soha technology onto the Company's platform as well as a trained technical workforce. The total amount of goodwill related to the acquisition of Soha expected to be deducted for tax purposes is $12.0 million. The allocation of the purchase price has not been finalized as the Company continues to assess the impact of relevant facts and circumstances.

Cyberfend

On December 15, 2016, the Company acquired Cyberfend, an innovator in bot and automation detection solutions for web and mobile environments, for $37.5 million in initial consideration and up to an additional $10.5 million upon the achievement of post-closing milestones. The acquisition is intended to further strengthen the Company's existing bot management and mitigation services. The Company allocated $38.8 million of the cost of the acquisition to goodwill and $6.5 million to acquired intangible assets. The total weighted average useful life of the intangible assets acquired from Cyberfend is 3.6 years. The value of the goodwill from the acquisition can be attributed to a number of business factors including a trained technical workforce and cost synergies expected to be realized. The total amount of goodwill related to the acquisition of Cyberfend expected to be deducted for tax purposes is $11.0 million. The allocation of the purchase price has not been finalized as the Company continues to assess the impact of relevant facts and circumstances.

2015 Acquisitions

Xerocole

On February 27, 2015, the Company acquired Xerocole, Inc. ("Xerocole"), a provider of recursive Domain Name System ("DNS") functionality, for $16.6 million in cash. The Company acquired Xerocole with a goal of expanding its existing Authoritative DNS products. The Company allocated $12.9 million of the cost of the acquisition to goodwill and $4.9 million to acquired intangible assets. The allocation of the purchase price was finalized in the third quarter of 2015. The total weighted average useful life of the intangible assets acquired from Xerocole is 8.8 years. The value of the goodwill from the acquisition can be attributed to a number of business factors including a trained technical workforce and cost synergies expected to be realized. The total amount of goodwill expected to be deducted for tax purposes is $2.7 million.

Octoshape

On April 6, 2015, the Company acquired all of the outstanding capital stock of Codemate A/S and its wholly-owned subsidiary Octoshape ApS (together, "Octoshape") in exchange for $107.0 million in cash. Octoshape is a cloud service provider focused on delivering broadcast, enterprise and carrier solutions. The goal of acquiring Octoshape was to make available for the Company's customers additional delivery and optimization technologies for video streams of over-the-top (often referred to as OTT) content and to enable the Company to more fully support Internet Protocol television ("IPTV") solutions. The consolidated financial statements include the operating results of Octoshape from the date of acquisition.

The purchase price allocation was finalized in the fourth quarter of 2015. The Company recorded a decrease of $0.5 million to goodwill upon the finalization of net working capital adjustments to the purchase price in the third quarter of 2015. The following table presents the final allocation of the purchase price for Octoshape (in thousands):



Total purchase consideration	$	107,047

Allocation of the purchase consideration:
Cash	$	664
Accounts receivable	1,976
Other current assets	393
Identifiable intangible assets	41,950
Goodwill	69,445
Deferred tax assets	5,230
Total assets acquired	119,658
Other current liabilities	(1,983		)
Current deferred revenue	(770		)
Deferred tax liabilities	(9,858		)
Total liabilities assumed	(12,611		)
Net assets acquired	$	107,047

The value of the goodwill can be attributed to a number of business factors, including a trained technical and sales workforce and cost synergies expected to be realized. The total amount of goodwill related to the acquisition of Octoshape expected to be deducted for tax purposes is $69.4 million.

The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except years):



	Gross Carrying Amount		Weighted Average Useful Life (in years)
Completed technologies	$	25,310	9.8
Customer-related intangible assets	16,560		11.8
Non-compete agreements	80		2.0
Total	$	41,950

The total weighted average amortization period for the intangible assets acquired from Octoshape is 10.6 years. The intangible assets are being amortized based upon the pattern in which the economic benefits of the intangible assets are being utilized.

Bloxx

On October 30, 2015, the Company acquired Bloxx Limited ("Bloxx"), a provider of Secure Web Gateway technology, for $18.7 million in cash. The acquisition is expected to provide the Company with technology to complement its cloud security strategy for protecting businesses against Internet vulnerabilities. The Company allocated $17.7 million of the cost of the acquisition to goodwill and $3.9 million to the acquired intangible assets. The allocation of the purchase price was finalized in the second quarter of 2016. The total weighted average useful life of the intangible assets acquired from Bloxx is 7.2 years. The value of the goodwill from the acquisition can be attributed to a number of business factors including a trained technical workforce and cost synergies expected to be realized. The total amount of goodwill related to the acquisition of Bloxx expected to be deducted for tax purposes is $17.7 million.

2014 Acquisitions

Prolexic Acquisition

On February 18, 2014, the Company acquired all of the outstanding capital stock of Prolexic Technologies, Inc. ("Prolexic") in exchange for $392.1 million in cash and the assumption of unvested stock options. The goal of acquiring Prolexic was to provide the Company's customers with a comprehensive portfolio of security solutions designed to defend an enterprise’s web and IP infrastructure against application-layer, network-layer and data center attacks delivered via the Internet. The consolidated financial statements include the operating results of Prolexic from the date of acquisition.

The purchase price allocation was finalized in the fourth quarter of 2014. The Company recorded an increase of $2.2 million to goodwill upon the finalization of measurement period adjustments related to certain tax-related assets and liabilities in the fourth quarter of 2014.

The following table presents the final allocation of the purchase price for Prolexic (in thousands):



Total purchase consideration	$	392,104

Allocation of the purchase consideration:
Cash	$	33,072
Accounts receivable	11,208
Property and equipment	12,225
Identifiable intangible assets	87,040
Goodwill	293,926
Deferred tax assets	16,340
Other current and long-term assets	5,664
Total assets acquired	459,475
Other current liabilities	(5,940		)
Current deferred revenue	(5,812		)
Deferred tax liabilities	(36,203		)
Debt, capital leases and other long-term liabilities	(19,416		)
Total liabilities assumed	(67,371		)
Net assets acquired	$	392,104

The value of the goodwill can be attributed to a number of business factors, including a trained technical and sales workforce and the fair value of cost synergies expected to be realized. The total amount of goodwill related to the acquisition of Prolexic expected to be deducted for tax purposes is $62.4 million.

The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except for years):



	Gross Carrying Amount		Weighted Average Useful Life (in years)
Completed technologies	$	26,800	6.9
Customer-related intangible assets	58,500		10.4
Non-compete agreements	940		3.0
Trademark	800		4.9
Total	$	87,040

The total weighted average amortization period for the intangible assets acquired from Prolexic is 9.2 years. The intangible assets are being amortized based upon the pattern in which the economic benefits of the intangible assets are being utilized.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

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+ Details

Accrued Expenses and Other Liabilities

12 Months Ended

Dec. 31, 2016

Accounts Payable and Accrued Liabilities, Current [Abstract]

Accrued Expenses and Other Liabilities

Accrued expenses consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016		December 31, 2015
Payroll and other related benefits	$	111,421	$	108,230
Bandwidth and co-location	61,084		48,228
Property, use and other taxes	52,959		47,364
Professional service fees	4,277		4,636
Other accrued expenses	9,036		7,708
Total	$	238,777	$	216,166

Other liabilities consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016		December 31, 2015
Deferred rent	$	29,668	$	32,876
Uncertain tax positions	73,231		53,641
Other long-term liabilities	15,792		6,751
Total	$	118,691	$	93,268

Commitments and Contingencies

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Lease Commitments

The Company leases its facilities under non-cancelable operating leases. These operating leases expire at various dates through December 2034 and generally require the payment of real estate taxes, insurance, maintenance and operating costs.

The minimum aggregate future obligations under non-cancelable leases as of December 31, 2016 were as follows (in thousands):



2017	$	53,410
2018	45,202
2019	44,586
2020	54,206
2021	54,934
Thereafter	533,088
Total	$	785,426

Rent expense for the years ended December 31, 2016, 2015 and 2014 was $50.3 million, $47.9 million and $39.9 million, respectively. The Company has entered into sublease agreements with tenants of various properties previously vacated by the Company. The amounts paid to the Company by these sublease tenants was $1.3 million, $3.6 million and $3.4 million for the years ended December 31, 2016, 2015 and 2014, respectively.

As of December 31, 2016, the Company had outstanding letters of credit in the amount of $6.8 million, primarily related to operating leases. The letters of credit remain in effect until the Company fulfills its obligations under these leases or as such obligations expire under the terms of the letters of credit.

Purchase Commitments

As of December 31, 2016, the Company had long-term commitments for bandwidth usage and co-location with various networks and ISPs and for asset purchases for network equipment. Additionally, as of December 31, 2016, the Company had entered into purchase orders with various vendors. The minimum future commitments as of December 31, 2016 were as follows (in thousands):



	Bandwidth and Co-location Commitments		Purchase Order Commitments
2017	$	105,451	$	137,642
2018	13,799		10,522
2019	6,368		1,827
2020	386		320
2021	193		320
Thereafter	—		—
Total	$	126,197	$	150,631

Legal Matters

The Company is party to various litigation matters that management considers routine and incidental to its business. Management does not expect the results of any of these routine actions to have a material effect on the Company’s business, results of operations, financial condition or cash flows.

In 2016, the Company completed an internal investigation, with the assistance of outside counsel, relating to improper sales practices by a former employee. The internal investigation included a review of compliance with the requirements of the U.S. Foreign Corrupt Practices Act and other applicable laws and regulations. In February 2015, the Company voluntarily contacted the Commission and Department of Justice to advise both agencies of this internal investigation. In June 2016, the Company signed a non-prosecution agreement with the Commission and agreed to disgorge $0.7 million to resolve this matter, including interest.

In July 2016, as part of the resolution of a patent infringement lawsuit filed by the Company against Limelight Networks, Inc. (“Limelight”) in 2006, the Company agreed to license to Limelight technology covered by certain of the Company’s patents. The terms of the agreement require Limelight to pay the Company $54.0 million in 12 equal installments over three years, beginning in August 2016. During the year ended December 31, 2016, the Company received $9.0 million under this agreement, which was recorded as a reduction to general and administrative expenses in the consolidated statement of income, with $0.4 million recorded as interest income.

In November 2015, Limelight filed a complaint in the U.S. District Court for the Eastern District of Virginia against the Company and XO Communications LLC (“XO”), alleging patent infringement by the two companies. The complaint alleges that the Company and XO infringed six of Limelight’s content delivery patents. The complaint seeks to recover from the Company and XO monetary damages based upon lost revenue due to infringing technology used by the companies. The Company has agreed to indemnify XO for damages it incurs in this matter. The Company has made counterclaims in the action against Limelight alleging that Limelight has infringed five of the Company’s content delivery patents, and the Company is seeking monetary damages based upon lost revenue due to the infringing technology used by Limelight. The case is scheduled for trial in May 2017. No provision with respect to this matter has been made in the Company’s consolidated financial statements. An estimate of the possible loss or range of loss cannot be made.

Indemnification

The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, the Company agrees to indemnify, hold harmless and reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company's business partners, vendors or customers, in connection with its provision of its services. Generally, these obligations are limited to claims relating to infringement of a patent, copyright or other intellectual property right or the Company’s negligence, willful misconduct or violation of law. Subject to applicable statutes of limitation, the term of these indemnification agreements is generally perpetual from the time of execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited; however, the Company carries insurance that covers certain third party claims relating to its services and activities and that could limit the Company’s exposure in that respect.

The Company has agreed to indemnify each of its officers and directors during his or her lifetime for certain events or occurrences that happen by reason of the fact that the officer or director is or was or has agreed to serve as an officer or director of the Company. The Company has director and officer insurance policies that may limit its exposure and may enable the Company to recover a portion of certain future amounts paid.

To date, the Company has not encountered material costs as a result of such indemnification obligations and has not accrued any related liabilities in its financial statements. In assessing whether to establish an accrual, the Company considers such factors as the degree of probability of an unfavorable outcome and the ability to make a reasonable estimate of the amount of loss.

Convertible Senior Notes

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Convertible Senior Notes

In February 2014, the Company issued $690.0 million in par value of convertible senior notes due 2019 (the "Notes"). The Notes are senior unsecured obligations of the Company, do not bear regular interest and mature on February 15, 2019, unless repurchased or converted prior to maturity.

At their option, holders may convert their Notes prior to the close of business on the business day immediately preceding August 15, 2018 only under the following circumstances:

•

during any calendar quarter commencing after the calendar quarter ended June 30, 2014 (and only during such calendar quarter), if the last reported sale price of the Company's common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; or


•	during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the conversion rate on each such trading day; or upon the occurrence of specified corporate events.

On or after August 15, 2018, holders may convert all or any portion of their Notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date, regardless of the foregoing circumstances.

Upon conversion, the Company, at its election, may pay or deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock. The initial conversion rate is 11.1651 shares of the Company's common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $89.56 per share, subject to adjustments in certain events, and represents a potential conversion into 7.7 million shares.

In accounting for the issuance of the Notes, the Company separated the Notes into liability and equity components.

The carrying cost of the liability component was calculated by measuring the fair value of a similar debt obligation that does

not have an associated convertible feature. The carrying amount of the equity component representing the conversion option

was determined by deducting the fair value of the liability component from the par value of the Notes. The difference between

the principal amount of the Notes and the proceeds allocated to the liability component (“debt discount”) is amortized to

interest expense using the effective interest method over the term of the Notes. The equity component is recorded in additional

paid-in capital in the consolidated balance sheet and will not be remeasured as long as it continues to meet the conditions for

equity classification.

In accounting for the transaction costs related to the issuance of the Notes, the Company allocated the total transaction

costs incurred to the liability and equity components based on their relative values. Transaction costs attributable to the liability

component are being amortized to interest expense over the term of the Notes, and transaction costs attributable to the equity

component are netted against the equity component of the Notes in stockholders’ equity.

The Notes consisted of the following components as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016			December 31, 2015
Liability component:
Principal	$	690,000		$	690,000
Less: debt discount and issuance costs, net of amortization	(49,913		)	(71,953		)
Net carrying amount	$	640,087		$	618,047

Equity component:	$	101,276		$	101,276

The estimated fair value of the Notes at December 31, 2016 was $721.4 million. The fair value was determined based

on the quoted price of the Notes in an inactive market on the last trading day of the reporting period and has been classified as

Level 2 within the fair value hierarchy. Based on the closing price of the Company's common stock of $66.68 on December 31, 2016, the value of the Notes if converted to common stock was less than the principal amount of $690.0 million.

The Company used $62.0 million of the proceeds from the offering to repurchase shares of its common stock, concurrent with the issuance of the Notes. The repurchase was made in accordance with the share repurchase program previously approved by the Board of Directors (Note 12). Additionally, $23.3 million of the proceeds was used for the net cost of convertible note hedge and warrant transactions. The remaining net proceeds are for working capital, share repurchases and other general corporate purposes, as well as for potential acquisitions and strategic transactions.

Note Hedge

To minimize the impact of potential dilution upon conversion of the Notes, the Company entered into convertible note hedge transactions with respect to its common stock in February 2014. The Company paid $101.3 million for the note hedge transactions. The note hedge transactions cover approximately 7.7 million shares of the Company’s common stock at a strike price that corresponds to the initial conversion price of the Notes, also subject to adjustment, and are exercisable upon conversion of the Notes. The note hedge transactions are intended to reduce dilution in the event of conversion of the Notes.

Warrants

Separately, in February 2014, the Company entered into warrant transactions, whereby the Company sold warrants to acquire, subject to anti-dilution adjustments, up to 7.7 million shares of the Company’s common stock at a strike price of approximately $104.49 per share. The Company received aggregate proceeds of $78.0 million from the sale of the warrants. The convertible note hedge and warrant transactions will generally have the effect of increasing the conversion price of the Notes to approximately $104.49 per share.

Interest Expense

The Notes do not bear regular interest, but have an effective interest rate of 3.2% attributable to the conversion feature. The following table sets forth total interest expense included in the consolidated statements of income related to the Notes for the years ended December 31, 2016 and 2015 (in thousands):



	2016			2015
Amortization of debt discount and issuance costs	$	22,040		$	21,280
Capitalization of interest expense	(3,402		)	(2,755		)
Total interest expense	$	18,638		$	18,525

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2016
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Stock Repurchase Program In October 2013, the Board of Directors authorized a $750.0 million share repurchase program, effective from October 2013 through December 2016. In February 2016, the Board of Directors authorized a $1.0 billion share repurchase program that superseded the October 2013 repurchase program and is effective from February 2016 through December 2018. The Company's goal for the share repurchase program is to offset the dilution created by its employee equity compensation programs and provide the flexibility to return capital to shareholders as business and market conditions warrant. During the years ended December 31, 2016, 2015 and 2014, the Company repurchased 7.0 million, 4.5 million and 4.6 million shares, respectively, of its common stock for $373.8 million, $302.6 million and $268.6 million, respectively, pursuant to the current repurchase program as well as prior ones approved by the Board of Directors. As of December 31, 2016, the Company had $694.5 million available for future purchases of shares under the current repurchase program. The Board of Directors authorized the retirement of all the outstanding shares of its treasury stock as of each of December 31, 2016, 2015 and 2014. The retired shares were returned to the number of authorized but unissued shares of the Company's common stock, and the retirement was recorded to additional paid-in capital.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

+ Details

Accumulated Other Comprehensive Loss

12 Months Ended

Dec. 31, 2016

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Accumulated Other Comprehensive Loss

The following table summarizes the changes in accumulated other comprehensive loss, which is reported as a component of stockholders' equity, for the year ended December 31, 2016 (in thousands):



	Foreign Currency Translation			Net Unrealized Gains (Losses) on Investments			Total
Balance as of January 1, 2016	$	(44,936	)	$	3,483		$	(41,453	)
Other comprehensive loss	(14,081		)	(688		)	(14,769		)
Balance as of December 31, 2016	$	(59,017	)	$	2,795		$	(56,222	)

The tax effect on accumulated unrealized gains on investments was insignificant as of December 31, 2016 and 2015. Amounts reclassified from accumulated other comprehensive loss to net income were insignificant for the year ended December 31, 2016.

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 220
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2016
Compensation Related Costs [Abstract]
Employee Benefit Plan	Employee Benefit Plan The Company has established a savings plan for its employees that is designed to be qualified under Section 401(k) of the Internal Revenue Code. Eligible employees are permitted to contribute to this plan through payroll deductions within statutory and plan limits. The Company contributed approximately $13.7 million, $13.1 million and $16.6 million of cash to the savings plan for the years ended December 31, 2016, 2015 and 2014, respectively, under a matching program.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-Based Compensation

Stock-Based Compensation

Equity Plans

In May 2013, the Company's stockholders approved the Akamai Technologies, Inc. 2013 Stock Incentive Plan (the "2013 Plan"). The 2013 Plan replaced the Akamai Technologies, Inc. 2009 Stock Incentive Plan (the "2009 Plan"), which in turn replaced the Akamai Technologies, Inc. 2006 Stock Incentive Plan, the Akamai Technologies, Inc. 2001 Stock Incentive Plan and the Akamai Technologies, Inc. 1998 Stock Incentive Plan (together with the 2009 Plan, the "Previous Plans"). The Company no longer issues equity awards under the Previous Plans, and they solely exist to satisfy outstanding equity awards previously granted under those plans. The 2013 Plan allows for the issuance of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units, other stock-based awards and cash-based awards up to 11.0 million shares of common stock to employees, officers, directors, consultants and advisers of the Company. Additionally, the Company may grant up to 3.8 million shares of common stock thereunder that were available for grant under the 2009 Plan immediately prior to stockholder approval of the 2013 Plan. Any shares of common stock that are currently outstanding under the Previous Plans that are terminated, canceled, surrendered or forfeited will become available to grant under the 2013 Plan. As of December 31, 2016, the Company had reserved approximately 6.6 million shares of common stock available for future issuance of equity awards under the 2013 Plan.

The Company has assumed certain stock option plans and the outstanding stock options of companies that it has acquired (“Assumed Plans”). Stock options outstanding as of the date of acquisition under the Assumed Plans were exchanged for the Company’s stock options and adjusted to reflect the appropriate conversion ratio as specified by the applicable acquisition agreement, but are otherwise administered in accordance with the terms of the Assumed Plans. Stock options under the Assumed Plans generally vest over four years and expire ten years from the date of grant.

The 1999 Employee Stock Purchase Plan ("1999 ESPP") permits eligible employees to purchase up to 1.5 million shares each June 1 and December 1, provided that the aggregate number of shares issued shall not exceed 20.0 million. The 1999 ESPP allows participants to purchase shares of common stock at a 15% discount from the fair market value of the stock as determined on specific dates at six-month intervals. During the years ended December 31, 2016, 2015 and 2014, the Company issued 0.9 million, 0.7 million and 0.7 million shares under the 1999 ESPP, respectively, with a weighted average purchase price per share of $46.23, $52.05 and $41.76, respectively. Total cash proceeds from the purchase of shares under the 1999 ESPP in the years ended December 31, 2016, 2015 and 2014 were $39.9 million, $34.8 million and $29.3 million, respectively. As of December 31, 2016, approximately $5.1 million had been withheld from employees for future purchases under the 1999 ESPP.

Stock-Based Compensation Expense

The following table summarizes the components of total stock-based compensation expense included in the Company’s consolidated statements of income for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016			2015			2014
Cost of revenue	$	18,287		$	14,145		$	11,934
Research and development	29,739			23,927			19,341
Sales and marketing	55,407			53,542			47,570
General and administrative	41,073			35,063			33,151
Total stock-based compensation	144,506			126,677			111,996
Provision for income taxes	(49,014		)	(49,033		)	(39,182		)
Total stock-based compensation, net of taxes	$	95,492		$	77,644		$	72,814

In addition to the amounts of stock-based compensation reported in the table above, the Company’s consolidated statements of income for the years ended December 31, 2016, 2015 and 2014 also include stock-based compensation reflected as a component of amortization of capitalized internal-use software; the additional stock-based compensation was $13.8 million, $12.7 million and $10.3 million, respectively, before taxes.

The Company uses the Black-Scholes option pricing model to determine the fair value of the Company’s stock option awards. This model requires the input of subjective assumptions, including expected stock price volatility and the estimated term of each award. The estimated fair value of the Company's stock-based awards, less expected forfeitures, is amortized over the awards’ vesting period on a straight-line basis. Expected volatilities are based on the Company’s historical stock price volatility and implied volatility from traded options in its stock. The Company uses historical data to estimate the expected term of options granted within the valuation model. The risk-free interest rate for periods commensurate with the expected term of the option is based on the U.S. Treasury yield rate in effect at the time of grant. The expected dividend yield is zero, as the Company currently does not pay a dividend and does not anticipate doing so in the future.

The Company did not grant any stock options during 2016 or 2015. The grant-date fair values of the Company's stock option awards granted during the year ended December 31, 2014 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:



	2014
Expected term (in years)	4.4
Risk-free interest rate	0.8	%
Expected volatility	40.4	%
Dividend yield	—	%

For the year ended December 31, 2014, the weighted average fair value of stock option awards granted was $49.67 per share.

The grant-date fair values of the Company's ESPP awards granted during the years ended December 31, 2016, 2015 and 2014 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:



	2016		2015		2014
Expected term (in years)	0.5		0.5		0.5
Risk-free interest rate	0.5	%	0.2	%	0.1	%
Expected volatility	36.2	%	28.0	%	33.5	%
Dividend yield	—	%	—	%	—	%

For the years ended December 31, 2016, 2015 and 2014, the weighted average fair value of ESPP awards granted was $14.54 per share, $15.63 per share and $12.64 per share, respectively.

As of December 31, 2016, total pre-tax unrecognized compensation cost for stock options, restricted stock units, deferred stock units and shares of common stock issued under the 1999 ESPP was $259.5 million. The expense is expected to be recognized through 2020 over a weighted average period of 2.0 years.

Stock Options

The following table summarizes stock option activity during the year ended December 31, 2016:



	Shares (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2016	1,524		$	32.39
Exercised	(643	)	28.17
Forfeited	(7	)	29.69
Outstanding at December 31, 2016	874		$	35.51	2.36	$	27,261
Exercisable at December 31, 2016	829		$	35.58	2.24	$	25,781
Vested or expected to vest December 31, 2016	870		$	35.52	2.35	$	27,123

The total pre-tax intrinsic value of options exercised during the years ended December 31, 2016, 2015 and 2014 was $18.3 million, $53.6 million and $45.8 million, respectively. The total fair value of options vested for the years ended December 31, 2016, 2015 and 2014 was $6.5 million, $10.3 million and $16.9 million, respectively.

The aggregate intrinsic value in the preceding table represents the total pre-tax intrinsic value, based on the Company’s closing stock price of $66.68 on December 31, 2016, that would have been received by the option holders had all option holders exercised their “in-the-money” options as of that date. The total number of shares issuable upon the exercise of “in-the-money” options exercisable as of December 31, 2016 was 0.8 million.

Deferred Stock Units

The Company has granted deferred stock units ("DSUs") to non-employee members of its Board of Directors. Each DSU represents the right to receive one share of the Company’s common stock upon vesting. The holder may elect to defer receipt of the vested shares of stock represented by the DSU for a period of at least one year but not more than ten years from the grant date. For those granted prior to 2014, DSUs vested 50% upon the first anniversary of the grant date, with the remaining 50% vesting in equal installments of 12.5% each quarter thereafter such that all DSUs vested in full at the end of two years from date of grant. Beginning in 2014, DSUs vest 100% on the first anniversary of the grant date. If a director has completed one year of Board service, vesting of 100% of the DSUs held by such director will accelerate at the time of his or her departure from the Board.

The following table summarizes the DSU activity for the year ended December 31, 2016:



	Units (in thousands)		Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016	146		$	45.42
Granted	46		50.72
Vested and distributed	(28	)	57.24
Outstanding at December 31, 2016	164		$	44.90

The total pre-tax intrinsic value of DSUs that were vested and distributed during the years ended December 31, 2016, 2015 and 2014 was $1.4 million, $10.7 million and $1.4 million, respectively. The total fair value of DSUs that were vested and distributed during the years ended December 31, 2016, 2015 and 2014 was $1.6 million, $4.9 million and $0.8 million, respectively. The grant-date fair value is calculated based upon the Company’s closing stock price on the date of grant. As of December 31, 2016, 46,000 DSUs were unvested, with an aggregate intrinsic value of approximately $3.1 million and a weighted average remaining contractual life of approximately 0.4 years. These units are expected to vest in May 2017.

Restricted Stock Units

The following table summarizes the different types of restricted stock units ("RSUs") granted by the Company during the year ended December 31, 2016 (in thousands):



	December 31, 2016
RSUs with service-based vesting conditions	3,873
RSUs with market-based vesting conditions	127
RSUs with performance-based vesting conditions	116
Total	4,116

RSUs represent the right to receive one share of the Company’s common stock upon vesting. RSUs are granted at the discretion of the Board of Directors, a committee thereof or, subject to defined limitations, the Chief Executive Officer of the Company, acting as a committee of one director, to whom such authority has been delegated. The Company has issued RSUs that vest based on the passage of time assuming continued service with the Company, RSUs that vest only upon the achievement of defined performance metrics tied primarily to revenue and income targets and other key financial performance indicators and RSUs that vest based upon total shareholder return ("TSR") measured against the benchmark TSR of a peer group.

For RSUs with service-based vesting conditions, the fair value is calculated based upon the Company’s closing stock price on the date of grant, and the stock-based compensation expense is being recognized over the vesting period. Most RSUs with service-based vesting provisions vest in installments over a three- or four-year period following the grant date.

Beginning in the first quarter of 2016, the Company granted RSUs with market-based vesting conditions to certain of its executive officers. The Company uses the Monte Carlo simulation model to determine the fair value of the Company’s RSUs based on TSR. This model requires the input of assumptions, including the estimated term of each award, the risk-free interest rate, historical stock price volatility of the Company's shares and historical stock price volatility of peer-company shares. The grant-date fair values of the Company's RSUs with market-based vesting conditions granted during the year ended December 31, 2016 were estimated using a Monte Carlo simulation model with the following assumptions:



	2016
Expected term (in years)	3.0
Risk-free interest rate	0.8	%
Akamai historical share price volatility	34.3	%
Average volatility of peer-company share price	27.6	%

For the years ended December 31, 2016, 2015 and 2014, management measured compensation expense for performance-based RSUs based upon a review of the Company’s expected achievement against specified financial performance targets. Such compensation cost is being recorded using a graded-vesting method for each series of grants of performance-based RSUs, to the extent management has deemed that such awards are probable of vesting based upon the expected achievement against the specified targets. On a periodic basis, management reviews the Company’s expected performance and adjusts the compensation cost, if needed, at such time.

The following table summarizes the RSU activity for the year ended December 31, 2016:



	Units (in thousands)		Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016	4,495		$	62.20
Granted	4,116		56.40
Vested	(2,374	)	59.13
Forfeited	(527	)	59.68
Outstanding at December 31, 2016	5,710		$	59.51

The total pre-tax intrinsic value of RSUs that vested during the years ended December 31, 2016, 2015 and 2014 was $128.5 million, $153.6 million and $145.6 million, respectively. The total fair value of RSUs that vested during the years ended December 31, 2016, 2015 and 2014 was $140.4 million, $105.3 million and $86.9 million, respectively. The grant-date fair value of each RSU is calculated based upon the Company’s closing stock price on the date of grant. As of December 31, 2016, 5.7 million RSUs were outstanding and unvested, with an aggregate intrinsic value of $380.7 million and a weighted average remaining vesting period of approximately 2.0 years. These RSUs are expected to vest on various dates through October 2020.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Income Taxes

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

The components of income before provision for income taxes were as follows for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016		2015		2014
U.S.	$	273,176	$	233,247	$	408,391
Foreign	186,270		223,377		71,385
Income before provision for income taxes	$	459,446	$	456,624	$	479,776

The provision for income taxes consisted of the following for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016			2015			2014
Current tax provision (benefit):
Federal	$	89,816		$	70,298		$	153,471
State	6,238			(1,750		)	4,978
Foreign	39,952			62,572			13,259
Deferred tax provision (benefit):
Federal	4,265			23,381			(13,073		)
State	(86		)	(742		)	(15,220		)
Foreign	3,916			(18,536		)	2,442
Change in valuation allowance	(787		)	(5		)	(29		)
Total	$	143,314		$	135,218		$	145,828

The Company includes the provision for income taxes incurred on intercompany sales as part of its current tax provision. The amount of the current year provision for income taxes required to be deferred is included as a deferred tax benefit. The amount of the current year deferral included in the Company’s deferred tax provision was a benefit of $9.1 million, $15.5 million and $24.3 million in the years ended December 31, 2016, 2015 and 2014, respectively.

The Company’s effective rate differed from the U.S. federal statutory rate as follows for the years ended December 31, 2016, 2015 and 2014:



	2016		2015		2014
U.S. federal income tax rate	35.0	%	35.0	%	35.0	%
State taxes	2.0		1.7		2.3
Nondeductible stock-based compensation	2.3		1.9		1.4
U.S. federal, state and foreign research and development credits	(3.3	)	(4.1	)	(3.2	)
Foreign earnings	(3.4	)	(4.6	)	(1.9	)
Domestic production activities deduction	(1.7	)	(1.2	)	(2.2	)
State software development activities benefit	—		—		(2.4	)
Other	0.3		0.9		1.4
	31.2	%	29.6	%	30.4	%

The components of the net deferred tax assets and liabilities and the related valuation allowance as of December 31, 2016 and 2015 were as follows (in thousands):



	2016			2015
Accrued bonus	$	18,390		$	13,161
Deferred revenue	10,055			11,334
Deferred rent	12,592			13,224
Stock-based compensation	32,030			31,705
Net operating losses	7,855			8,855
Unrealized losses	1,862			1,421
Tax credit carryforwards	23,629			22,918
License income	16,932			—
Other	7,048			5,989
Deferred tax assets	130,393			108,607
Depreciation and amortization	(10,470		)	(10,848		)
Acquired intangible assets	(44,788		)	(37,923		)
Internal-use software development costs capitalized	(77,375		)	(66,807		)
Deferred tax liabilities	(132,633		)	(115,578		)
Valuation allowance	(430		)	(1,217		)
Net deferred tax liabilities	$	(2,670	)	$	(8,188	)

During the years ended December 31, 2016 and 2015, the valuation allowance related to the Company's deferred tax assets decreased by an insignificant amount. As of December 31, 2016 and 2015, the Company had the following NOL and credit carryforwards (in thousands, except for years):



	2016		2015		Expirations at Various Dates Through:
NOL carryforwards:
Federal	$	16,500	$	21,500	2029
State	11,400		28,200		2034
Foreign	—		—
Federal and state research and development tax credit carryforwards	41,500		39,800		2031

The Company's U.S. federal NOL carryforwards relate to acquisitions completed during 2012. As of December 31, 2016, the Company had no foreign tax credit carryforwards.

As of December 31, 2016, undistributed earnings of non-U.S. subsidiaries totaled $470.4 million. No provision for U.S. income and foreign withholding taxes has been made for these permanently reinvested foreign earnings because it is expected that such earnings will be reinvested indefinitely. If these earnings were distributed to the U.S. in the form of dividends or otherwise, it would be included in the Company's U.S. taxable income. The amount of unrecognized deferred income tax liability related to these earnings is $89.4 million.

The following is a rollforward of the Company’s unrecognized tax benefits for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016			2015			2014
Balance at beginning of year	$	65,290		$	33,320		$	24,651
Gross increases — tax positions of prior periods	6,391			11,238			12,925
Gross increases — current-period tax positions	6,252			27,043			2,106
Gross decreases — tax positions of prior periods	(6,778		)	(5,996		)	(6,362		)
Gross decreases — settlements	(2,038		)	(315		)	—
Balance at end of year	$	69,117		$	65,290		$	33,320

As of December 31, 2016, 2015 and 2014, the Company had approximately $77.1 million, $72.3 million and $41.1 million, respectively, of total unrecognized tax benefits, including $13.7 million, $10.0 million, and $7.7 million of accrued interest and penalties as of December 31, 2016, 2015 and 2014, respectively. Interest and penalties related to unrecognized tax benefits are recorded in the provision for income taxes and were $3.9 million, $2.2 million and $1.8 million for the years ended December 31, 2016, 2015 and 2014, respectively. If recognized, the aggregate amount of unrecognized tax benefits would have resulted in a reduction of income tax expense, impacting the effective income tax rate.

As of December 31, 2016, the Company believes it is reasonably possible that $15.8 million of its unrecognized tax benefits may be recognized by the end of 2017 as a result of the expiration of local statutes of limitations. Certain state and foreign income tax returns from 2011 through 2014 are currently under audit in those jurisdictions, including an audit in the Commonwealth of Massachusetts. The Company has reserved for those positions that are not more likely than not of being sustained.

Generally, in the U.S. federal and state taxing jurisdictions, tax periods in which certain loss and credit carryovers are generated remain open for audit until such time as the limitation period ends for the year in which such losses or credits are utilized. In major foreign jurisdictions, tax years after 2012 are open for examination.

Net Income per Share

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Net Income per Share

Basic net income per share is computed using the weighted average number of common shares outstanding during the applicable period. Diluted net income per share is computed using the weighted average number of common shares outstanding during the period, plus the dilutive effect of potential common stock. Potential common stock consists of shares issuable pursuant to stock options, RSUs, DSUs, convertible senior notes and warrants issued by the Company. The dilutive effect of outstanding awards and convertible securities is reflected in diluted earnings per share by application of the treasury stock method.

The following table sets forth the components used in the computation of basic and diluted net income per share for the years ended December 31, 2016, 2015 and 2014 (in thousands, except per share data):



	2016		2015		2014
Numerator:
Net income	$	316,132	$	321,406	$	333,948
Denominator:
Shares used for basic net income per share	174,917		178,391		178,279
Effect of dilutive securities:
Stock options	384		794		1,221
RSUs and DSUs	914		1,230		1,686
Convertible senior notes	—		—		—
Warrants related to issuance of convertible senior notes	—		—		—
Shares used for diluted net income per share	176,215		180,415		181,186
Basic net income per share	$	1.81	$	1.80	$	1.87
Diluted net income per share	$	1.79	$	1.78	$	1.84

For the years ended December 31, 2016, 2015 and 2014, certain potential outstanding shares from stock options, service-based RSUs, convertible notes and warrants were excluded from the computation of diluted net income per share because the effect of including these items was anti-dilutive. Additionally, certain performance-based RSUs were excluded from the computation of diluted net income per share because the underlying performance conditions for such RSUs had not been met as of these dates. The number of potentially outstanding shares excluded from the computation of diluted net income per share for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016	2015	2014
Stock options	58	22	402
Service-based RSUs	2,262	660	786
Performance-based RSUs	690	1,007	570
Convertible senior notes	7,704	7,704	7,704
Warrants related to issuance of convertible senior notes	7,704	7,704	7,704
Total shares excluded from computation	18,418	17,097	17,166

Segment and Geographic Information	12 Months Ended
Segment and Geographic Information	Dec. 31, 2016
Segment Reporting [Abstract]
Segment and Geographic Information	Segment and Geographic Information The Company’s chief operating decision-maker is the chief executive officer and the executive management team. As of December 31, 2016, the Company operated in one industry segment: providing cloud services for delivering, optimizing and securing content and business applications over the Internet. The Company is not organized by market and is managed and operated as one business. A single management team that reports to the chief executive officer comprehensively manages the entire business. The Company does not operate any material separate lines of business or separate business entities with respect to its services. Accordingly, the Company does not accumulate discrete financial information with respect to separate divisions and does not have separate operating or reportable segments. The Company deploys its servers into networks worldwide. As of December 31, 2016, the Company had approximately $297.8 million and $231.8 million of net property and equipment, excluding internal-use software, located in the U.S. and foreign locations, respectively. As of December 31, 2015, the Company had approximately $298.9 million and $227.8 million of net property and equipment, excluding internal-use software, located in the U.S. and foreign locations, respectively. The Company sells its services and licenses through a sales force located both domestically and abroad. Revenue derived from operations outside of the U.S. is determined based on the country in which the sale originated and was $720.0 million, $593.0 million and $531.9 million for the years ended December 31, 2016, 2015 and 2014, respectively. Other than the U.S., no single country accounted for 10% or more of the Company’s total revenue for any reported period.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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+ Details

Quarterly Financial Results (unaudited)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Results (unaudited)



(in thousands, except per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Year ended December 31, 2016:
Revenue	$	567,725	$	572,135	$	584,065	$	616,124
Cost of revenue (exclusive of amortization of acquired intangible assets)	194,736		206,323		204,467		203,475
Net income	74,858		73,635		76,000		91,639
Basic net income per share	0.42		0.42		0.44		0.53
Diluted net income per share	0.42		0.42		0.43		0.52
Year ended December 31, 2015:
Revenue	$	526,536	$	540,723	$	551,030	$	579,159
Cost of revenue (exclusive of amortization of acquired intangible assets)	169,294		179,910		183,204		193,212
Net income	77,746		67,200		88,040		88,420
Basic net income per share	0.44		0.38		0.49		0.50
Diluted net income per share	0.43		0.37		0.49		0.49

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2016
Summary of Significant Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The Company prepares its consolidated financial statements in conformity with accounting principles generally accepted in the United States of America. These principles require management to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the amounts disclosed in the related notes to the consolidated financial statements. Actual results and outcomes may differ materially from management’s estimates, judgments and assumptions. Significant estimates, judgments and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, valuation and impairment of investments and marketable securities, valuation and useful lives of acquired intangible assets, useful lives and realizability of long-lived assets, capitalized internal-use software development costs, income tax reserves and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. The effects of material revisions in estimates are reflected in the consolidated financial statements prospectively from the date of the change in estimate.
Cash, Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities Cash and cash equivalents consist of cash held in bank deposit accounts and short-term, highly-liquid investments with remaining maturities of three months or less at the date of purchase. Marketable securities consist of corporate, government and other securities. Securities having remaining maturities of less than one year from the date of the balance sheet are classified as short-term, and those with maturities of more than one year from the date of the balance sheet are classified as long-term in the consolidated balance sheet. The Company classifies its debt and equity investments with readily determinable market values as available-for-sale. These investments are classified as marketable securities on the consolidated balance sheets and are carried at fair market value, with unrealized gains and losses considered to be temporary in nature and reported as accumulated other comprehensive loss, a separate component of stockholders’ equity. The Company reviews all investments for reductions in fair value that are other-than-temporary. When such reductions occur, the cost of the investment is adjusted to fair value through recording a loss on investments in the consolidated statements of income. Gains and losses on investments are calculated on the basis of specific identification. Marketable securities are considered to be impaired when a decline in fair value below cost basis is determined to be other-than-temporary. The Company periodically evaluates whether a decline in fair value below cost basis is other-than-temporary by considering available evidence regarding these investments including, among other factors: the duration of the period that, and extent to which, the fair value is less than cost basis; the financial health and business outlook of the issuer, including industry and sector performance and operational and financing cash flow factors; overall market conditions and trends and the Company’s intent and ability to retain its investment in the security for a period of time sufficient to allow for an anticipated recovery in market value. Once a decline in fair value is determined to be other-than-temporary, a write-down is recorded and a new cost basis in the security is established. Assessing the above factors involves inherent uncertainty. Write-downs, if recorded, could be materially different from the actual market performance of marketable securities in the Company’s portfolio if, among other things, relevant information related to the marketable securities was not publicly available or other factors not considered by the Company would have been relevant to the determination of impairment.
Accounts Receivable and Related Reserves	Accounts Receivable and Related Reserves The Company’s accounts receivable balance includes unbilled amounts that represent revenue recorded for customers that are typically billed monthly in arrears. The Company records reserves against its accounts receivable balance. These reserves consist of allowances for doubtful accounts and reserves for cash-basis customers. Increases and decreases in the allowance for doubtful accounts are included as a component of general and administrative expense in the consolidated statements of income. The Company’s reserve for cash-basis customers increases as services are provided to customers where collection is no longer assured. Increases to the reserve for cash-basis customers are recorded as reductions of revenue. The reserve decreases and revenue is recognized when and if cash payments are received. Estimates are used in determining these reserves and are based upon the Company’s review of outstanding balances on a customer-specific, account-by-account basis. The allowance for doubtful accounts is based upon a review of customer receivables from prior sales with collection issues where the Company no longer believes that the customer has the ability to pay for services previously provided. The Company also performs ongoing credit evaluations of its customers. If such an evaluation indicates that payment is no longer reasonably assured for services provided, any future services provided to that customer will result in the creation of a cash-basis reserve until the Company receives consistent payments. The Company does not have any off-balance sheet credit exposure related to its customers.
Concentrations of Credit Risk	Concentrations of Credit Risk The amounts reflected in the consolidated balance sheets for accounts receivable, other current assets, accounts payable, accrued liabilities and other current liabilities approximate their fair values due to their short-term maturities. The Company maintains the majority of its cash, cash equivalents and marketable securities with major financial institutions that the Company believes to be of high credit standing. The Company believes that, as of December 31, 2016, its concentration of credit risk related to cash equivalents and marketable securities was not significant. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which the Company makes substantial sales. The Company’s customer base consists of a large number of geographically-dispersed customers diversified across several industries. To reduce risk, the Company routinely assesses the financial strength of its customers. Based on such assessments, the Company believes that its accounts receivable credit risk exposure is limited. For the years ended December 31, 2016, 2015 and 2014, no customer accounted for more than 10% of total revenue. As of December 31, 2016, 2015 and 2014, no customer had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2016, its concentration of credit risk related to accounts receivable was not significant.
Fair Value of Financial Measurements	Fair Value of Financial Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company has certain financial assets and liabilities recorded at fair value, principally cash equivalents and short- and long-term marketable securities that have been classified as Level 1, 2 or 3 within the fair value hierarchy. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the reporting date. Fair values determined by Level 2 inputs utilize data points other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Fair values determined by Level 3 inputs are based on unobservable data points for the asset or liability.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost, net of accumulated depreciation and amortization. Property and equipment generally include purchases of items with a per-unit value greater than $1,000 and an estimated useful life greater than one year. Depreciation and amortization are computed on a straight-line basis over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the related lease terms or their estimated useful lives. The Company periodically reviews the estimated useful lives of property and equipment, and any changes to the estimated useful lives are recorded prospectively from the date of the change. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are removed from the accounts, and any resulting gain or loss is included in income from operations. Repairs and maintenance costs are expensed as incurred.
Goodwill, Acquired Intangible Assets and Long-Lived Assets	Goodwill, Acquired Intangible Assets and Long-Lived Assets Goodwill is the amount by which the cost of acquired net assets in a business combination exceeds the fair value of the net identifiable assets on the date of purchase and is carried at its historical cost. The Company tests goodwill for impairment on an annual basis or more frequently if events or changes in circumstances indicate that the asset might be impaired. The Company performs its impairment test of goodwill as of December 31. As of December 31, 2016, 2015 and 2014, the fair value of the Company's reporting unit was substantially in excess of the carrying value. The tests did not result in an impairment to goodwill during the years ended December 31, 2016, 2015 and 2014. Acquired intangible assets consist of completed technologies, customer relationships, trademarks and trade names, non-compete agreements and acquired license rights. Acquired intangible assets, other than goodwill, are amortized over their estimated useful lives based upon the estimated economic value derived from the related intangible asset. Long-lived assets, including property and equipment and acquired intangible assets, are reviewed for impairment whenever events or changes in circumstances, such as service discontinuance, technological obsolescence, significant decreases in the Company’s market capitalization, facility closures or work-force reductions indicate that the carrying amount of the long-lived asset may not be recoverable. When such events occur, the Company compares the carrying amount of the asset to the undiscounted expected future cash flows related to the asset. If this comparison indicates that an impairment is present, the amount of the impairment is calculated as the difference between the carrying amount and the fair value of the asset.
Revenue Recognition	Revenue Recognition The Company recognizes service revenue in accordance with the authoritative guidance for revenue recognition, including guidance on revenue arrangements with multiple deliverables. Revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, the service is performed and collectability of the resulting receivable is reasonably assured. The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. These contracts generally commit the customer to a minimum of monthly, quarterly or annual level of usage and specify the rate at which the customer must pay for actual usage above the monthly, quarterly or annual minimum. For contracts with a monthly commitment, the Company recognizes the monthly minimum as revenue each month, provided that an enforceable contract has been signed by both parties, the service has been delivered to the customer, the fee for the service is fixed or determinable and collection is reasonably assured. Should a customer’s usage of the Company's services exceed the monthly, quarterly or annual minimum, the Company recognizes revenue for such excess in the period of additional usage. For annual or other non-monthly period revenue commitments, the Company recognizes revenue monthly based upon the customer’s actual usage each month of the commitment period and only recognizes any remaining committed amount for the applicable period in the last month thereof. The Company typically charges its customers an integration fee when the services are first activated. Integration fees are recorded as deferred revenue and recognized as revenue ratably over the estimated life of the customer arrangement. The Company also derives revenue from services sold as discrete, non-recurring events or based solely on usage. For these services, the Company recognizes revenue once the event or usage has occurred. When more than one element is contained in a revenue arrangement, the Company determines the fair value for each element in the arrangement based on vendor-specific objective evidence (“VSOE”) for each respective element, including any renewal rates for services contractually offered to the customer. Elements typically included in the Company's multiple element arrangements consist of its core services – the delivery of content, applications and software over the Internet – as well as mobile and security solutions and enterprise professional services. These elements have value to the customer on a stand-alone basis in that they can be sold separately by another vendor. Generally, there is no right of return relative to these services. The Company typically uses VSOE to determine the fair value of its separate elements. All stand-alone sales of professional services are reviewed to establish the average stand-alone selling price for those services. For the Company's core services, the fair value is the price charged for a single deliverable on a per unit basis when it is sold separately. For arrangements in which the Company is unable to establish VSOE, third party evidence ("TPE") of the fair value of each element is determined based upon the price charged when the element is sold separately by another vendor. For arrangements in which the Company is unable to establish VSOE or TPE for each element, the Company uses the best estimate of selling price ("BESP") to determine the fair value of the separate deliverables. The Company estimates BESP based upon a management-approved listing of unit pricing for all solutions and pre-established discount levels for each solution that takes into consideration volume, geography and industry lines. The Company allocates arrangement consideration across the multiple elements using the relative selling price method. At the inception of a customer contract, the Company makes an assessment as to that customer’s ability to pay for the services provided. The Company bases its assessment on a combination of factors, including the successful completion of a credit check or financial review, its collection experience with the customer and other forms of payment assurance. Upon the completion of these steps, the Company recognizes revenue monthly in accordance with its revenue recognition policy. If the Company subsequently determines that collection from the customer is not reasonably assured, the Company records an allowance for doubtful accounts and bad debt expense for all of that customer’s unpaid invoices and ceases recognizing revenue for continued services provided until cash is received from the customer. Changes in the Company’s estimates and judgments about whether collection is reasonably assured would change the timing of revenue or amount of bad debt expense that the Company recognizes. The Company also sells its services through reseller channels. Assuming all other revenue recognition criteria are met, the Company recognizes revenue from reseller arrangements based on the reseller’s contracted non-refundable minimum purchase commitments over the term of the contract, plus amounts sold by the reseller to its customers in excess of the minimum commitments. Amounts attributable to this excess usage are recognized as revenue in the period in which the service is provided. From time to time, the Company enters into contracts to sell its services or license its technology to unrelated enterprises at or about the same time that it enters into contracts to purchase products or services from the same enterprises. If the Company concludes that these contracts were negotiated concurrently, the Company records as revenue only the net cash received from the vendor, unless the product or service received has a separate identifiable benefit and the fair value of the vendor’s product or service can be established objectively. The Company may from time to time resell licenses or services of third parties. The Company records revenue for these transactions on a gross basis when the Company has risk of loss related to the amounts purchased from the third party and the Company adds value to the license or service, such as by providing maintenance or support for such license or service. If these conditions are present, the Company recognizes revenue when all other revenue recognition criteria are satisfied. Deferred revenue represents amounts billed to customers for which revenue has not been recognized. Deferred revenue primarily consists of the unearned portion of monthly billed service fees, prepayments made by customers for future periods, deferred integration and activation set-up fees and amounts billed under customer arrangements with extended payment terms.
Cost of Revenues	Cost of Revenue Cost of revenue consists primarily of fees paid to network providers for bandwidth and to third party network data centers for housing servers, also known as co-location costs. Cost of revenue also includes employee costs for services delivery and network operation, build-out and support of the Company's network; network storage costs; cost of software licenses; depreciation of network equipment used to deliver the Company’s services; amortization of network-related internal-use software; and costs for the production of live events. The Company enters into contracts for bandwidth with third party network providers with terms typically ranging from several months to five years. These contracts generally commit the Company to pay minimum monthly fees plus additional fees for bandwidth usage above the committed level. In some circumstances, Internet service providers (“ISPs”) make rack space available for the Company’s servers and access to their bandwidth at a discount or no cost. In exchange, the ISP and its customers benefit by receiving content through a local Company server resulting in better content delivery. The Company does not consider these relationships to represent the culmination of an earnings process. Accordingly, the Company does not recognize as revenue the value to the ISPs associated with the use of the Company’s servers, nor does the Company recognize as expense the value of the rack space and bandwidth received at discounted or no cost.
Research and Development Costs and Capitalized Internal-Use Software	Research and Development Costs and Capitalized Internal-Use Software Research and development costs consist primarily of payroll and related personnel costs for the design, development, deployment, testing and enhancement of the Company’s services and network. Costs incurred in the development of the Company’s services are expensed as incurred, except certain internal-use software development costs eligible for capitalization. Capitalized costs include external consulting fees, payroll and payroll-related costs and stock-based compensation for employees in the Company’s development and information technology groups who are directly associated with, and who devote time to, the Company’s internal-use software projects. Capitalization begins when the planning stage is complete and the Company commits resources to the software project, and continues during the application development stage. Capitalization ceases when the software has been tested and is ready for its intended use. Costs incurred during the planning, training and post-implementation stages of the software development life-cycle are expensed as incurred. The Company amortizes completed internal-use software that is used on its network to cost of revenue over its estimated useful life.
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation The Company recognizes compensation costs for all stock-based payment awards made to employees based upon the awards’ grant-date fair value. The stock-based payment awards include stock options, restricted stock units, deferred stock units and employee stock purchases related to the Company’s employee stock purchase plan. For stock options, the Company has selected the Black-Scholes option-pricing model to determine the fair value of stock option awards. For stock awards with market-based vesting conditions, the Company uses a Monte Carlo simulation to determine the fair value of the award. For stock options, restricted stock units and deferred stock units that contain only a service-based vesting feature, the Company recognizes compensation cost on a straight-line basis over the award's vesting period. For awards with a performance condition-based vesting feature, the Company recognizes compensation cost on a graded-vesting basis over the award's expected vesting period, commencing when achievement of the performance condition is deemed probable. In addition, for awards that vest and become exercisable only upon achievement of specified performance conditions, the Company makes judgments and estimates each quarter about the probability that such performance conditions will be met or achieved. Any changes to those estimates that the Company makes from time to time may have a significant impact on the stock-based compensation expense recorded and could materially impact the Company’s results of operations.
Foreign Currency Translation and Forward Currency Contracts	Foreign Currency Translation and Forward Currency Contracts The assets and liabilities of the Company's subsidiaries are translated at the applicable exchange rate as of the balance sheet date, and revenue and expenses are translated at an average rate over the period. Resulting currency translation adjustments are recorded as a component of accumulated other comprehensive loss, a separate component of stockholders’ equity. Gains and losses on inter-company and other non-functional currency transactions are recorded in other income (expense), net. The Company enters into short-term foreign currency forward contracts to offset foreign exchange gains and losses generated by the re-measurement of certain assets and liabilities recorded in non-functional currencies. Changes in the fair value of these derivatives, as well as re-measurement gains and losses, are recognized in current earnings in other income (expense), net. As of December 31, 2016 and 2015, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2016, 2015 and 2014 were immaterial. The Company's foreign currency forward contracts may be exposed to credit risk to the extent that its counterparties are unable to meet the terms of the agreements. The Company seeks to minimize counterparty credit (or repayment) risk by entering into transactions only with major financial institutions of investment grade credit rating.
Taxes	Taxes The Company's provision for income taxes is comprised of a current and a deferred portion. The current income tax provision is calculated as the estimated taxes payable or refundable on tax returns for the current year. The deferred income tax provision is calculated as the estimated future tax effects attributable to temporary differences and carryforwards using expected tax rates in effect during the years in which the differences are expected to reverse or the carryforwards are expected to be realized. The Company currently has net deferred tax assets consisting of net operating loss (“NOL”) carryforwards, tax credit carryforwards and deductible temporary differences. Management periodically weighs the positive and negative evidence to determine if it is more likely than not that some or all of the deferred tax assets will be realized. The Company has recorded certain tax reserves to address potential exposures involving its income tax and sales and use tax positions. These potential tax liabilities result from the varying application of statutes, rules, regulations and interpretations by different taxing jurisdictions. The Company's estimate of the value of its tax reserves contains assumptions based on past experiences and judgments about the interpretation of statutes, rules and regulations by taxing jurisdictions. It is possible that the costs of the ultimate tax liability or benefit from these matters may be more or less than the amount the Company estimated. Uncertainty in income taxes is recognized in the Company's consolidated financial statements using a two-step process. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The Company has elected to account for the indirect income tax effects of stock-based compensation as provision for income taxes. This primarily includes the impact of the research and development tax credit and the domestic production activities deduction.
Newly-Adopted Accounting Pronouncements and Recent Accounting Pronouncements	Newly-Adopted Accounting Pronouncements In April 2015, the Financial Accounting Standards Board (“FASB”) issued updated guidance to simplify the presentation of debt issuance costs on the balance sheets. This guidance moved debt issuance costs from the assets section of the balance sheet to the liabilities section as a direct deduction from the carrying amount of the debt issued. The Company retrospectively adopted the guidance on January 1, 2016. The prior period consolidated balance sheet presented, as of December 31, 2015, was revised to reclassify $6.2 million of debt issuance costs included in other assets to convertible senior notes. This had the impact of reducing the Company's total assets and total liabilities by $6.2 million, as of December 31, 2015. This reclassification did not have a material impact on the Company's consolidated financial statements. In September 2015, the FASB issued updated guidance that eliminates the requirement that an acquirer in a business combination account for measurement period adjustments retrospectively. In an effort to reduce complexity in financial reporting, the new guidance requires that the cumulative impact of a measurement period adjustment, including the impact on prior periods, be recognized in the reporting period in which the adjustment is identified. The standard was effective for and adopted by the Company on January 1, 2016. This guidance did not have an impact on the Company's consolidated financial statements as the measurement periods for the Company's 2015 acquisitions were closed as of December 31, 2015. Recent Accounting Pronouncements In May 2014, the FASB issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step model for recognizing revenue from contracts with customers. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard can be adopted using one of two methods: retrospectively to each prior period presented or a modified retrospective application by recognizing a cumulative-effect adjustment as a component of equity as of the date of adoption. The updated guidance modifies certain judgments and estimates that the Company currently makes as it relates to recognizing revenue. Upon adoption of the new revenue standard, integration fee revenue that was previously recognized ratably over the estimated life of the customer arrangement will be recognized when integration has been completed, which will have the effect of accelerating revenue from integration fees. In addition, the Company currently establishes a reserve for cash basis customers if collectability is not reasonably assured and recognizes revenue as cash is collected. Upon adoption of the new standard, revenue will be recognized for those customers when collectability becomes probable, rather than as cash is collected. The Company is also assessing the impact of capitalizing costs associated with obtaining customer contracts, specifically commission and incentive payments. Currently, these payments are expensed in the period they are incurred. Under the updated guidance, these payments will be deferred on the Company's consolidated balance sheets and amortized over the expected life of the customer contract. This standard will be effective for the Company on January 1, 2018. The Company continues to evaluate the potential impact of adopting this new accounting guidance on its consolidated financial statements. In February 2016, the FASB issued guidance that requires companies to present assets and liabilities arising from leases with a term greater than 12 months on the consolidated balance sheets. The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize right-of-use assets and lease liabilities on the balance sheet and requiring disclosure of key information about leasing arrangements. This will impact all leases, which include leases for real estate and co-location facilities, among other arrangements currently under evaluation. The Company plans to adopt this standard in the first quarter of 2019 and expects to record significant right-of-use assets and lease liabilities on its consolidated balance sheets. In March 2016, the FASB issued guidance that is intended to simplify aspects of how share-based payments are accounted for and presented in financial statements. This guidance requires that entities record all tax effects of share-based payments at settlement or expiration through the income statement. The standard also amends how windfall tax benefits are recognized, the minimum statutory tax withholding requirements and how entities elect to recognize share-based payment forfeitures. In addition, this guidance impacts the presentation of cash flows related to excess tax benefits by no longer requiring separate presentation as a financing activity apart from other operating income tax cash flows. This guidance was effective for the Company beginning on January 1, 2017. Upon adoption on a prospective basis, the Company is recognizing excess tax benefits in its provision for income taxes rather than as additional paid-in capital. In addition, the Company expects to adopt the presentation requirements related to the excess tax benefit in its cash flows on a retrospective basis, which will result in an increase to cash flows from operating activities of $5.5 million and $29.3 million with a corresponding decrease to cash flows from financing activities for the years ended December 31, 2016 and 2015, respectively. Finally, the Company expects to continue estimating forfeitures in determining the amount of compensation cost. In June 2016, the FASB issued guidance that introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new "expected loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. This guidance will be effective for the Company on January 1, 2020. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements. In October 2016, the FASB issued guidance that requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. This guidance will be effective for the Company on January 1, 2018 and is to be applied on a modified retrospective basis through a recognizing cumulative-effect adjustment as a component of equity as of the date of adoption. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of Marketable Securities

The following is a summary of available-for-sale marketable securities held as of December 31, 2016 and 2015 (in thousands):



			Gross Unrealized					Aggregate Fair Value		Classification on Balance Sheet
	Amortized Cost									Short-Term Marketable Securities		Long-Term Marketable Securities
As of December 31, 2016	Amortized Cost		Gains		Losses					Short-Term Marketable Securities		Long-Term Marketable Securities
Commercial paper	$	40,965	$	—	$	(45	)	$	40,920	$	40,920	$	—
Corporate bonds	984,650		123		(3,697		)	981,076		418,495		562,581
U.S. government agency obligations	267,473		35		(1,366		)	266,142		53,157		212,985
	$	1,293,088	$	158	$	(5,108	)	$	1,288,138	$	512,572	$	775,566

As of December 31, 2015
Commercial paper	$	2,491	$	—	$	(4	)	$	2,487	$	2,487	$	—
Corporate bonds	995,100		73		(3,365		)	991,808		432,585		559,223
U.S. government agency obligations	239,587		41		(575		)	239,053		25,016		214,037
	$	1,237,178	$	114	$	(3,944	)	$	1,233,348	$	460,088	$	773,260

Schedule of Fair Value Measurement

The following table details the fair value measurements within the fair value hierarchy of the Company’s financial assets and liabilities as of December 31, 2016 and 2015 (in thousands):



	Total Fair Value			Fair Value Measurements at Reporting Date Using
	Total Fair Value			Level 1		Level 2		Level 3
As of December 31, 2016
Cash Equivalents and Marketable Securities:
Money market funds	$	8,726		$	8,726	$	—	$	—
Commercial paper	40,920			—		40,920		—
Corporate bonds	981,076			—		981,076		—
U.S. government agency obligations	266,142			—		266,142		—
Mutual funds	4,022			4,022		—		—
	$	1,300,886		$	12,748	$	1,288,138	$	—

Liabilities:
Contingent consideration obligation related to completed acquisitions	$	(7,100	)	$	—	$	—	$	(7,100	)

As of December 31, 2015
Cash Equivalents and Marketable Securities:
Money market funds	$	1,250		$	1,250	$	—	$	—
Commercial paper	2,487			—		2,487		—
Corporate bonds	991,808			—		991,808		—
U.S. government agency obligations	239,053			—		239,053		—
Mutual funds	1,414			1,414		—		—
	$	1,236,012		$	2,664	$	1,233,348	$	—

Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs

The following table reflects the activity for the Company’s major classes of liabilities measured at fair value using Level 3 inputs for the years ended December 31, 2016 and 2015 (in thousands):



	Other Liabilities: Contingent Consideration Obligation
Balance, January 1, 2015	$	(900	)
Fair value adjustment to Velocius contingent consideration included in general and administrative expense	(100		)
Achievement of final milestone related to Velocius contingent consideration	1,000
Balance, December 31, 2015	$	—
Contingent consideration obligation related to Soha Systems, Inc. acquisition	(1,600		)
Contingent consideration obligation related to Cyberfend, Inc. acquisition	(5,500		)
Balance, December 31, 2016	$	(7,100	)

Schedule of Contractual Maturities of Marketable Securities and Other Investment Related Assets

Contractual maturities of the Company’s available-for-sale marketable securities held as of December 31, 2016 and 2015 were as follows (in thousands):



	December 31, 2016		December 31, 2015
Due in 1 year or less	$	512,572	$	460,088
Due after 1 year through 5 years	775,566		773,260
	$	1,288,138	$	1,233,348

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2016

Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]

Schedule of Accounts Receivable

Net accounts receivable consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016			December 31, 2015
Trade accounts receivable	$	260,976		$	262,885
Unbilled accounts receivable	113,765			124,878
Gross accounts receivable	374,741			387,763
Allowance for doubtful accounts	(829		)	(906		)
Reserve for cash-basis customers	(5,316		)	(6,458		)
Total accounts receivable reserves	(6,145		)	(7,364		)
Accounts receivable, net	$	368,596		$	380,399

Schedule of Activity in the Accounts Receivable Reserves

A summary of activity in the accounts receivable reserves for the years ended December 31, 2016, 2015 and 2014, is as follows (in thousands):



	2016			2015			2014
Beginning balance	$	7,364		$	9,023		$	3,703
Charges to income from operations	49,677			37,870			32,293
Collections from cash basis customers and write-offs	(50,896		)	(39,529		)	(26,973		)
Ending balance	$	6,145		$	7,364		$	9,023

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2016

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016		December 31, 2015
Prepaid income taxes	$	25,161	$	31,045
Other prepaid expenses	40,532		43,751
Other current assets	38,610		48,432
Total	$	104,303	$	123,228

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment consisted of the following as of December 31, 2016 and 2015 (dollars in thousands):



	December 31, 2016			December 31, 2015			Estimated Useful Life in Years
Computer and networking equipment	$	1,170,471		$	1,046,739		3-7
Purchased software	51,727			46,509			3-10
Furniture and fixtures	41,968			35,212			5
Office equipment	24,497			21,108			3-5
Leasehold improvements	139,991			119,466			1-16
Internal-use software	656,053			546,520			2-7
Property and equipment, gross	2,084,707			1,815,554
Accumulated depreciation and amortization	(1,283,690		)	(1,062,374		)
Property and equipment, net	$	801,017		$	753,180

Goodwill and Acquired Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of the Changes in the Carrying Amount of Goodwill

The changes in the carrying amount of goodwill for the years ended December 31, 2016 and 2015 were as follows (in thousands):



	2016			2015
Beginning balance	$	1,150,244		$	1,051,294
Acquisition of Xerocole, Inc.	—			12,859
Acquisition of Codemate A/S	—			69,445
Acquisition of Bloxx Limited	—			17,694
Acquisition of Concord Systems, Inc.	1,079			—
Acquisition of Soha Systems, Inc.	43,515			—
Acquisition of Cyberfend, Inc.	38,754			—
Foreign currency translation	(5,089		)	(1,048		)
Ending balance	$	1,228,503		$	1,150,244

Schedule of Acquired Intangible Assets

Acquired intangible assets that are subject to amortization consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016							December 31, 2015
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Completed technologies	$	119,091	$	(50,823	)	$	68,268	$	120,791	$	(58,633	)	$	62,158
Customer-related intangible assets	192,810		(114,209		)	78,601		191,710		(102,872		)	88,838
Non-compete agreements	5,030		(3,775		)	1,255		6,540		(3,374		)	3,166
Trademarks and trade names	3,700		(2,361		)	1,339		3,700		(1,767		)	1,933
Acquired license rights	490		(490		)	—		490		(490		)	—
Total	$	321,121	$	(171,658	)	$	149,463	$	323,231	$	(167,136	)	$	156,095

The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except for years):



	Gross Carrying Amount		Weighted Average Useful Life (in years)
Completed technologies	$	26,800	6.9
Customer-related intangible assets	58,500		10.4
Non-compete agreements	940		3.0
Trademark	800		4.9
Total	$	87,040

The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except years):



	Gross Carrying Amount		Weighted Average Useful Life (in years)
Completed technologies	$	25,310	9.8
Customer-related intangible assets	16,560		11.8
Non-compete agreements	80		2.0
Total	$	41,950

Business Acquisitions and Divestitures (Tables)

12 Months Ended

Dec. 31, 2016

Business Combinations [Abstract]

Schedule of Purchase Price Allocation

The following table presents the final allocation of the purchase price for Octoshape (in thousands):



Total purchase consideration	$	107,047

Allocation of the purchase consideration:
Cash	$	664
Accounts receivable	1,976
Other current assets	393
Identifiable intangible assets	41,950
Goodwill	69,445
Deferred tax assets	5,230
Total assets acquired	119,658
Other current liabilities	(1,983		)
Current deferred revenue	(770		)
Deferred tax liabilities	(9,858		)
Total liabilities assumed	(12,611		)
Net assets acquired	$	107,047

The following table presents the final allocation of the purchase price for Prolexic (in thousands):



Total purchase consideration	$	392,104

Allocation of the purchase consideration:
Cash	$	33,072
Accounts receivable	11,208
Property and equipment	12,225
Identifiable intangible assets	87,040
Goodwill	293,926
Deferred tax assets	16,340
Other current and long-term assets	5,664
Total assets acquired	459,475
Other current liabilities	(5,940		)
Current deferred revenue	(5,812		)
Deferred tax liabilities	(36,203		)
Debt, capital leases and other long-term liabilities	(19,416		)
Total liabilities assumed	(67,371		)
Net assets acquired	$	392,104

Schedule of Acquired Intangible Assets

Acquired intangible assets that are subject to amortization consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016							December 31, 2015
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Completed technologies	$	119,091	$	(50,823	)	$	68,268	$	120,791	$	(58,633	)	$	62,158
Customer-related intangible assets	192,810		(114,209		)	78,601		191,710		(102,872		)	88,838
Non-compete agreements	5,030		(3,775		)	1,255		6,540		(3,374		)	3,166
Trademarks and trade names	3,700		(2,361		)	1,339		3,700		(1,767		)	1,933
Acquired license rights	490		(490		)	—		490		(490		)	—
Total	$	321,121	$	(171,658	)	$	149,463	$	323,231	$	(167,136	)	$	156,095

The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except for years):



	Gross Carrying Amount		Weighted Average Useful Life (in years)
Completed technologies	$	26,800	6.9
Customer-related intangible assets	58,500		10.4
Non-compete agreements	940		3.0
Trademark	800		4.9
Total	$	87,040

The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except years):



	Gross Carrying Amount		Weighted Average Useful Life (in years)
Completed technologies	$	25,310	9.8
Customer-related intangible assets	16,560		11.8
Non-compete agreements	80		2.0
Total	$	41,950

Accrued Expenses and Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2016

Accounts Payable and Accrued Liabilities, Current [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016		December 31, 2015
Payroll and other related benefits	$	111,421	$	108,230
Bandwidth and co-location	61,084		48,228
Property, use and other taxes	52,959		47,364
Professional service fees	4,277		4,636
Other accrued expenses	9,036		7,708
Total	$	238,777	$	216,166

Other liabilities consisted of the following as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016		December 31, 2015
Deferred rent	$	29,668	$	32,876
Uncertain tax positions	73,231		53,641
Other long-term liabilities	15,792		6,751
Total	$	118,691	$	93,268

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Minimum Aggregate Future Obligations Under Non-Cancelable Leases

The minimum aggregate future obligations under non-cancelable leases as of December 31, 2016 were as follows (in thousands):



2017	$	53,410
2018	45,202
2019	44,586
2020	54,206
2021	54,934
Thereafter	533,088
Total	$	785,426

Schedule of Long-Term Commitments

The minimum future commitments as of December 31, 2016 were as follows (in thousands):



	Bandwidth and Co-location Commitments		Purchase Order Commitments
2017	$	105,451	$	137,642
2018	13,799		10,522
2019	6,368		1,827
2020	386		320
2021	193		320
Thereafter	—		—
Total	$	126,197	$	150,631

- Definition

Tabular disclosure of a lessee's leasing arrangements including: (1) the basis on which contingent rental payments are determined, (2) the existence and terms of renewal or purchase options and escalation clauses, (3) restrictions imposed by lease arrangements, such as those concerning dividends, additional debt, and further leasing, (4) rent holidays, rent concessions, or leasehold improvement incentives and unusual provisions or conditions. Disclosure may also include the specific period used to amortize material leasehold improvements made at the inception of the lease or during the lease term. Additionally, for operating leases having initial or remaining noncancelable lease terms in excess of one year: (a) future minimum rental payments required as of the date of the latest balance sheet presented, in the aggregate and for each of the five succeeding fiscal years, (b) the total of minimum rentals to be received in the future under noncancelable subleases as of the date of the latest balance sheet presented, and (c) for all operating leases, rental expense for each period for which an income statement is presented, with separate amounts for minimum rentals, contingent rentals, and sublease rentals. Rental payments under leases with terms of a month or less that were not renewed need not be included.

+ References + Details

Convertible Senior Notes (Tables)

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Schedule of Convertible Senior Notes

The Notes consisted of the following components as of December 31, 2016 and 2015 (in thousands):



	December 31, 2016			December 31, 2015
Liability component:
Principal	$	690,000		$	690,000
Less: debt discount and issuance costs, net of amortization	(49,913		)	(71,953		)
Net carrying amount	$	640,087		$	618,047

Equity component:	$	101,276		$	101,276

Schedule of Interest Expense

The following table sets forth total interest expense included in the consolidated statements of income related to the Notes for the years ended December 31, 2016 and 2015 (in thousands):



	2016			2015
Amortization of debt discount and issuance costs	$	22,040		$	21,280
Capitalization of interest expense	(3,402		)	(2,755		)
Total interest expense	$	18,638		$	18,525

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

+ Details

Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Dec. 31, 2016

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The following table summarizes the changes in accumulated other comprehensive loss, which is reported as a component of stockholders' equity, for the year ended December 31, 2016 (in thousands):



	Foreign Currency Translation			Net Unrealized Gains (Losses) on Investments			Total
Balance as of January 1, 2016	$	(44,936	)	$	3,483		$	(41,453	)
Other comprehensive loss	(14,081		)	(688		)	(14,769		)
Balance as of December 31, 2016	$	(59,017	)	$	2,795		$	(56,222	)

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock Based Compensation Expense



	2016			2015			2014
Cost of revenue	$	18,287		$	14,145		$	11,934
Research and development	29,739			23,927			19,341
Sales and marketing	55,407			53,542			47,570
General and administrative	41,073			35,063			33,151
Total stock-based compensation	144,506			126,677			111,996
Provision for income taxes	(49,014		)	(49,033		)	(39,182		)
Total stock-based compensation, net of taxes	$	95,492		$	77,644		$	72,814

Schedule of Stock Options Granted Black Scholes

The grant-date fair values of the Company's stock option awards granted during the year ended December 31, 2014 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:



	2014
Expected term (in years)	4.4
Risk-free interest rate	0.8	%
Expected volatility	40.4	%
Dividend yield	—	%

Schedule of Assumptions Used

The grant-date fair values of the Company's RSUs with market-based vesting conditions granted during the year ended December 31, 2016 were estimated using a Monte Carlo simulation model with the following assumptions:



	2016
Expected term (in years)	3.0
Risk-free interest rate	0.8	%
Akamai historical share price volatility	34.3	%
Average volatility of peer-company share price	27.6	%



	2016		2015		2014
Expected term (in years)	0.5		0.5		0.5
Risk-free interest rate	0.5	%	0.2	%	0.1	%
Expected volatility	36.2	%	28.0	%	33.5	%
Dividend yield	—	%	—	%	—	%

Schedule of Summary of Stock Option Activity

The following table summarizes stock option activity during the year ended December 31, 2016:



	Shares (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2016	1,524		$	32.39
Exercised	(643	)	28.17
Forfeited	(7	)	29.69
Outstanding at December 31, 2016	874		$	35.51	2.36	$	27,261
Exercisable at December 31, 2016	829		$	35.58	2.24	$	25,781
Vested or expected to vest December 31, 2016	870		$	35.52	2.35	$	27,123

Schedule Of Deferred Stock Units Activity

The following table summarizes the DSU activity for the year ended December 31, 2016:



	Units (in thousands)		Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016	146		$	45.42
Granted	46		50.72
Vested and distributed	(28	)	57.24
Outstanding at December 31, 2016	164		$	44.90

Schedule of Restricted Stock Units by Type

The following table summarizes the different types of restricted stock units ("RSUs") granted by the Company during the year ended December 31, 2016 (in thousands):



	December 31, 2016
RSUs with service-based vesting conditions	3,873
RSUs with market-based vesting conditions	127
RSUs with performance-based vesting conditions	116
Total	4,116

Schedule of Restricted Stock Units Activity

The following table summarizes the RSU activity for the year ended December 31, 2016:



	Units (in thousands)		Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016	4,495		$	62.20
Granted	4,116		56.40
Vested	(2,374	)	59.13
Forfeited	(527	)	59.68
Outstanding at December 31, 2016	5,710		$	59.51

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Components of Income Before Tax

The components of income before provision for income taxes were as follows for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016		2015		2014
U.S.	$	273,176	$	233,247	$	408,391
Foreign	186,270		223,377		71,385
Income before provision for income taxes	$	459,446	$	456,624	$	479,776

Schedule of Provision for Income Tax

The provision for income taxes consisted of the following for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016			2015			2014
Current tax provision (benefit):
Federal	$	89,816		$	70,298		$	153,471
State	6,238			(1,750		)	4,978
Foreign	39,952			62,572			13,259
Deferred tax provision (benefit):
Federal	4,265			23,381			(13,073		)
State	(86		)	(742		)	(15,220		)
Foreign	3,916			(18,536		)	2,442
Change in valuation allowance	(787		)	(5		)	(29		)
Total	$	143,314		$	135,218		$	145,828

Schedule of Difference Between Effective and Statutory

The Company’s effective rate differed from the U.S. federal statutory rate as follows for the years ended December 31, 2016, 2015 and 2014:



	2016		2015		2014
U.S. federal income tax rate	35.0	%	35.0	%	35.0	%
State taxes	2.0		1.7		2.3
Nondeductible stock-based compensation	2.3		1.9		1.4
U.S. federal, state and foreign research and development credits	(3.3	)	(4.1	)	(3.2	)
Foreign earnings	(3.4	)	(4.6	)	(1.9	)
Domestic production activities deduction	(1.7	)	(1.2	)	(2.2	)
State software development activities benefit	—		—		(2.4	)
Other	0.3		0.9		1.4
	31.2	%	29.6	%	30.4	%

Net Deferred Tax and Valuation Allowance

The components of the net deferred tax assets and liabilities and the related valuation allowance as of December 31, 2016 and 2015 were as follows (in thousands):



	2016			2015
Accrued bonus	$	18,390		$	13,161
Deferred revenue	10,055			11,334
Deferred rent	12,592			13,224
Stock-based compensation	32,030			31,705
Net operating losses	7,855			8,855
Unrealized losses	1,862			1,421
Tax credit carryforwards	23,629			22,918
License income	16,932			—
Other	7,048			5,989
Deferred tax assets	130,393			108,607
Depreciation and amortization	(10,470		)	(10,848		)
Acquired intangible assets	(44,788		)	(37,923		)
Internal-use software development costs capitalized	(77,375		)	(66,807		)
Deferred tax liabilities	(132,633		)	(115,578		)
Valuation allowance	(430		)	(1,217		)
Net deferred tax liabilities	$	(2,670	)	$	(8,188	)

Schedule of Operating Loss Carryforwards

As of December 31, 2016 and 2015, the Company had the following NOL and credit carryforwards (in thousands, except for years):



	2016		2015		Expirations at Various Dates Through:
NOL carryforwards:
Federal	$	16,500	$	21,500	2029
State	11,400		28,200		2034
Foreign	—		—
Federal and state research and development tax credit carryforwards	41,500		39,800		2031

Unrecognized Tax Benefits

The following is a rollforward of the Company’s unrecognized tax benefits for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016			2015			2014
Balance at beginning of year	$	65,290		$	33,320		$	24,651
Gross increases — tax positions of prior periods	6,391			11,238			12,925
Gross increases — current-period tax positions	6,252			27,043			2,106
Gross decreases — tax positions of prior periods	(6,778		)	(5,996		)	(6,362		)
Gross decreases — settlements	(2,038		)	(315		)	—
Balance at end of year	$	69,117		$	65,290		$	33,320

Net Income per Share (Tables)

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Schedule of Components Used in Diluted and Basic Income Per Common Share



	2016		2015		2014
Numerator:
Net income	$	316,132	$	321,406	$	333,948
Denominator:
Shares used for basic net income per share	174,917		178,391		178,279
Effect of dilutive securities:
Stock options	384		794		1,221
RSUs and DSUs	914		1,230		1,686
Convertible senior notes	—		—		—
Warrants related to issuance of convertible senior notes	—		—		—
Shares used for diluted net income per share	176,215		180,415		181,186
Basic net income per share	$	1.81	$	1.80	$	1.87
Diluted net income per share	$	1.79	$	1.78	$	1.84

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The number of potentially outstanding shares excluded from the computation of diluted net income per share for the years ended December 31, 2016, 2015 and 2014 (in thousands):



	2016	2015	2014
Stock options	58	22	402
Service-based RSUs	2,262	660	786
Performance-based RSUs	690	1,007	570
Convertible senior notes	7,704	7,704	7,704
Warrants related to issuance of convertible senior notes	7,704	7,704	7,704
Total shares excluded from computation	18,418	17,097	17,166

Quarterly Financial Results (unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Unaudited Quarterly Financial Results



(in thousands, except per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Year ended December 31, 2016:
Revenue	$	567,725	$	572,135	$	584,065	$	616,124
Cost of revenue (exclusive of amortization of acquired intangible assets)	194,736		206,323		204,467		203,475
Net income	74,858		73,635		76,000		91,639
Basic net income per share	0.42		0.42		0.44		0.53
Diluted net income per share	0.42		0.42		0.43		0.52
Year ended December 31, 2015:
Revenue	$	526,536	$	540,723	$	551,030	$	579,159
Cost of revenue (exclusive of amortization of acquired intangible assets)	169,294		179,910		183,204		193,212
Net income	77,746		67,200		88,040		88,420
Basic net income per share	0.44		0.38		0.49		0.50
Diluted net income per share	0.43		0.37		0.49		0.49

Nature of Business and Basis of Presentation - Narrative (Details)	12 Months Ended
	Dec. 31, 2016 network segment country server
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of servers (more than) \| server	200,000
Number of networks (more than) \| network	1,600
Number of countries with networks (more than) \| country	131
Number of operating segments \| segment	1

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2016
Summary of Significant Accounting Policies [Line Items]
Property and equipment per unit value, minimum	$ 1,000
Property, plant and equipment, estimated useful life, minimum (in years)	1 year
Minimum percentage of tax benefit to be recognized (in percentage)	50.00%
Increase to cash flows from operating activities	$ 866,298,000	$ 764,151,000	$ 658,070,000
Decrease to cash flows from financing activities	$ 354,265,000	$ 267,728,000	$ (436,027,000)
Sales \| Customer concentration risk \| No Customer [Member]
Summary of Significant Accounting Policies [Line Items]
Concentration risk percent (more than)	10.00%	10.00%	10.00%
Accounts receivable \| Customer concentration risk \| No Customer [Member]
Summary of Significant Accounting Policies [Line Items]
Concentration risk percent (more than)	10.00%	10.00%
Accounting Standards Update 2016-09 [Member]
Summary of Significant Accounting Policies [Line Items]
Increase to cash flows from operating activities	$ 5,500,000	$ 29,300,000
Decrease to cash flows from financing activities	$ 5,500,000	$ 29,300,000
Other Assets [Member] \| Adjustments for New Accounting Pronouncement [Member]
Summary of Significant Accounting Policies [Line Items]
Amount of deferred financing costs reclassified				$ (6,200,000)
Convertible Senior Notes [Member] \| Adjustments for New Accounting Pronouncement [Member]
Summary of Significant Accounting Policies [Line Items]
Amount of deferred financing costs reclassified				$ 6,200,000

Fair Value Measurements - Narrative (Details) $ in Millions	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position for more than 12 months	$ 13.8

Fair Value Measurements - Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	$ 1,293,088	$ 1,237,178
Gross unrealized gains	158	114
Gross unrealized losses	(5,108)	(3,944)
Available-for-sale securities	1,288,138	1,233,348
Short-term marketable securities	512,572	460,088
Long-term marketable securities	775,566	773,260
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	40,965	2,491
Gross unrealized gains	0	0
Gross unrealized losses	(45)	(4)
Available-for-sale securities	40,920	2,487
Short-term marketable securities	40,920	2,487
Long-term marketable securities	0	0
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	984,650	995,100
Gross unrealized gains	123	73
Gross unrealized losses	(3,697)	(3,365)
Available-for-sale securities	981,076	991,808
Short-term marketable securities	418,495	432,585
Long-term marketable securities	562,581	559,223
U.S. government agency obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	267,473	239,587
Gross unrealized gains	35	41
Gross unrealized losses	(1,366)	(575)
Available-for-sale securities	266,142	239,053
Short-term marketable securities	53,157	25,016
Long-term marketable securities	$ 212,985	$ 214,037

Fair Value Measurements - Schedule of Fair Value Measurement (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Cash Equivalents and Marketable Securities:
Available-for-sale securities	$ 1,288,138	$ 1,233,348
Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	40,920	2,487
Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	981,076	991,808
U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	266,142	239,053
Level 1
Cash Equivalents and Marketable Securities:
Assets, fair value	12,748	2,664
Contingent consideration obligation related to completed acquisitions	0
Level 1 \| Money market funds
Cash Equivalents and Marketable Securities:
Cash equivalents	8,726	1,250
Level 1 \| Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 1 \| Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 1 \| U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 1 \| Mutual funds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	4,022	1,414
Level 2
Cash Equivalents and Marketable Securities:
Assets, fair value	1,288,138	1,233,348
Contingent consideration obligation related to completed acquisitions	0
Level 2 \| Money market funds
Cash Equivalents and Marketable Securities:
Cash equivalents	0	0
Level 2 \| Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	40,920	2,487
Level 2 \| Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	981,076	991,808
Level 2 \| U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	266,142	239,053
Level 2 \| Mutual funds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 3
Cash Equivalents and Marketable Securities:
Assets, fair value	0	0
Contingent consideration obligation related to completed acquisitions	(7,100)
Level 3 \| Money market funds
Cash Equivalents and Marketable Securities:
Cash equivalents	0	0
Level 3 \| Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 3 \| Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 3 \| U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Level 3 \| Mutual funds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Total Fair Value
Cash Equivalents and Marketable Securities:
Assets, fair value	1,300,886	1,236,012
Contingent consideration obligation related to completed acquisitions	(7,100)
Total Fair Value \| Money market funds
Cash Equivalents and Marketable Securities:
Cash equivalents	8,726	1,250
Total Fair Value \| Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	40,920	2,487
Total Fair Value \| Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	981,076	991,808
Total Fair Value \| U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	266,142	239,053
Total Fair Value \| Mutual funds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	$ 4,022	$ 1,414

Fair Value Measurements - Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, Other Liabilities:Contingent Consideration Obligation	$ 0	$ (900)
Ending balance, Other Liabilities:Contingent Consideration Obligation	(7,100)	0
Velocius
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value adjustment to contingent consideration for acquisition included in general and administrative expense		(100)
Contingent consideration settlements		$ 1,000
Soha Systems, Inc.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration obligations	(1,600)
Cyberfend, Inc.
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration obligations	$ (5,500)

Fair Value Measurements - Schedule of Contractual Maturities of Marketable Securities and Other Investment Related Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Due in 1 year or less	$ 512,572	$ 460,088
Due after 1 year through 5 years	775,566	773,260
Available-for-sale securities	$ 1,288,138	$ 1,233,348

Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 374,741	$ 387,763
Allowance for doubtful accounts	(829)	(906)
Reserve for cash-basis customers	(5,316)	(6,458)
Total accounts receivable reserves	(6,145)	(7,364)
Accounts receivable, net	368,596	380,399
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	260,976	262,885
Unbilled Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 113,765	$ 124,878

Accounts Receivable - Activity in Accounts Receivable Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ 7,364	$ 9,023	$ 3,703
Charges to income from operations	49,677	37,870	32,293
Collections from cash basis customers	(50,896)	(39,529)	(26,973)
Ending balance	$ 6,145	$ 7,364	$ 9,023

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid income taxes	$ 25,161	$ 31,045
Other prepaid expenses	40,532	43,751
Other current assets	38,610	48,432
Total	$ 104,303	$ 123,228

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, software and equipment depreciation, amortization expense	$ 307.7	$ 272.5	$ 215.3
Capitalization of stock-based compensation	23.1	17.9	$ 15.2
Disposal of property plant and equipment	$ 93.4	$ 48.7

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,084,707	$ 1,815,554
Accumulated depreciation and amortization	(1,283,690)	(1,062,374)
Property and equipment, net	801,017	753,180
Computer and networking equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,170,471	1,046,739
Purchased software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	51,727	46,509
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 41,968	35,212
Estimated useful life (in years)	5 years
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 24,497	21,108
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	139,991	119,466
Internal-use software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 656,053	$ 546,520
Minimum \| Computer and networking equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Minimum \| Purchased software
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Minimum \| Office equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Minimum \| Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	1 year
Minimum \| Internal-use software
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	2 years
Maximum \| Computer and networking equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	7 years
Maximum \| Purchased software
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	10 years
Maximum \| Office equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Maximum \| Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	16 years
Maximum \| Internal-use software
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	7 years

Goodwill and Acquired Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 26,642	$ 27,067	$ 32,057
Future amortization expense, 2017	29,200
Future amortization expense, 2018	26,400
Future amortization expense, 2019	25,000
Future amortization expense, 2020	21,100
Future amortization expense, 2021	$ 16,600

Goodwill and Acquired Intangible Assets - Schedule of the Changes in the Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Changes in the carrying amount of goodwill
Beginning balance	$ 1,150,244	$ 1,051,294
Foreign currency translation	(5,089)	(1,048)
Ending balance	1,228,503	1,150,244
Xerocole, Inc.
Changes in the carrying amount of goodwill
Additions	0	12,859
Codemate A/S
Changes in the carrying amount of goodwill
Additions	0	69,445
Bloxx Limited
Changes in the carrying amount of goodwill
Additions	0	17,694
Concord Systems, Inc.
Changes in the carrying amount of goodwill
Additions	1,079	0
Soha Systems, Inc.
Changes in the carrying amount of goodwill
Additions	43,515	0
Cyberfend, Inc.
Changes in the carrying amount of goodwill
Additions	$ 38,754	$ 0

Goodwill and Acquired Intangible Assets - Schedule of Other Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 321,121	$ 323,231
Accumulated amortization	(171,658)	(167,136)
Net carrying amount	149,463	156,095
Completed technologies
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	119,091	120,791
Accumulated amortization	(50,823)	(58,633)
Net carrying amount	68,268	62,158
Customer-related intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	192,810	191,710
Accumulated amortization	(114,209)	(102,872)
Net carrying amount	78,601	88,838
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	5,030	6,540
Accumulated amortization	(3,775)	(3,374)
Net carrying amount	1,255	3,166
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	3,700	3,700
Accumulated amortization	(2,361)	(1,767)
Net carrying amount	1,339	1,933
Acquired license rights
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	490	490
Accumulated amortization	(490)	(490)
Net carrying amount	$ 0	$ 0

Business Acquisitions and Divestitures (Details) - USD ($) $ in Thousands								3 Months Ended		12 Months Ended
	Dec. 15, 2016	Oct. 03, 2016	Sep. 23, 2016	Oct. 30, 2015	Apr. 06, 2015	Feb. 27, 2015	Feb. 18, 2014	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 03, 2016
Business Acquisition [Line Items]
Acquisition related costs										$ 1,700	$ 1,800	$ 4,200
Goodwill									$ 1,051,294	$ 1,228,503	$ 1,150,244	$ 1,051,294
Concord Systems, Inc.
Business Acquisition [Line Items]
Cash transferred			$ 3,000
Identifiable intangible assets			2,800
Goodwill			$ 1,100
Weighted average useful life			7 years
Soha Systems, Inc.
Business Acquisition [Line Items]
Purchase consideration		$ 55,000
Maximum potential payout of the contingent consideration													$ 5,000
Goodwill, expected tax deductible amount													$ 12,000
Identifiable intangible assets		10,700
Goodwill		$ 43,500
Weighted average useful life		4 years 8 months 12 days
Cyberfend, Inc.
Business Acquisition [Line Items]
Purchase consideration	$ 37,500
Maximum potential payout of the contingent consideration	10,500
Goodwill, expected tax deductible amount	11,000
Identifiable intangible assets	6,500
Goodwill	$ 38,800
Weighted average useful life	3 years 7 months
Xerocole, Inc.
Business Acquisition [Line Items]
Purchase consideration						$ 16,600
Goodwill, expected tax deductible amount						2,700
Identifiable intangible assets						4,900
Goodwill						$ 12,900
Weighted average useful life						8 years 9 months 18 days
Octoshape
Business Acquisition [Line Items]
Purchase consideration					$ 107,047
Measurement period adjustment, increase (decrease) in goodwill								$ (500)
Goodwill, expected tax deductible amount					69,400
Cash					664
Accounts receivable					1,976
Other current assets					393
Identifiable intangible assets					41,950
Goodwill					69,445
Deferred tax assets					5,230
Total assets acquired					119,658
Other current liabilities					(1,983)
Current deferred revenue					(770)
Deferred tax liabilities					(9,858)
Total liabilities assumed					(12,611)
Net assets acquired					107,047
Gross carrying amount of intangible assets					$ 41,950
Weighted average useful life					10 years 7 months 6 days
Octoshape \| Completed technologies
Business Acquisition [Line Items]
Gross carrying amount of intangible assets					$ 25,310
Weighted average useful life					9 years 9 months
Octoshape \| Customer-related intangible assets
Business Acquisition [Line Items]
Gross carrying amount of intangible assets					$ 16,560
Weighted average useful life					11 years 9 months
Octoshape \| Non-compete agreements
Business Acquisition [Line Items]
Gross carrying amount of intangible assets					$ 80
Weighted average useful life					2 years
Bloxx
Business Acquisition [Line Items]
Purchase consideration				$ 18,700
Goodwill, expected tax deductible amount				17,700
Identifiable intangible assets				3,900
Goodwill				$ 17,700
Weighted average useful life				7 years 2 months 12 days
Prolexic
Business Acquisition [Line Items]
Purchase consideration							$ 392,104
Measurement period adjustment, increase (decrease) in goodwill									$ 2,200
Goodwill, expected tax deductible amount							62,400
Cash							33,072
Accounts receivable							11,208
Property and equipment							12,225
Identifiable intangible assets							87,040
Goodwill							293,926
Deferred tax assets							16,340
Other current and long-term assets							5,664
Total assets acquired							459,475
Other current liabilities							(5,940)
Current deferred revenue							(5,812)
Deferred tax liabilities							(36,203)
Other liabilities assumed							(19,416)
Total liabilities assumed							(67,371)
Net assets acquired							392,104
Gross carrying amount of intangible assets							$ 87,040
Weighted average useful life							9 years 2 months 12 days
Prolexic \| Completed technologies
Business Acquisition [Line Items]
Gross carrying amount of intangible assets							$ 26,800
Weighted average useful life							6 years 11 months
Prolexic \| Customer-related intangible assets
Business Acquisition [Line Items]
Gross carrying amount of intangible assets							$ 58,500
Weighted average useful life							10 years 5 months
Prolexic \| Non-compete agreements
Business Acquisition [Line Items]
Gross carrying amount of intangible assets							$ 940
Weighted average useful life							3 years
Prolexic \| Trademarks and trade names
Business Acquisition [Line Items]
Gross carrying amount of intangible assets							$ 800
Weighted average useful life							4 years 11 months

Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts Payable and Accrued Liabilities, Current [Abstract]
Payroll and other related benefits	$ 111,421	$ 108,230
Bandwidth and co-location	61,084	48,228
Property, use and other taxes	52,959	47,364
Professional service fees	4,277	4,636
Other accrued expenses	9,036	7,708
Total	238,777	216,166
Deferred rent	29,668	32,876
Uncertain tax positions	73,231	53,641
Other long-term liabilities	15,792	6,751
Total	$ 118,691	$ 93,268

Commitments and Contingencies - Minimum Aggregate Future Obligations Under Non-cancelable Leases and Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
2017	$ 53,410
2018	45,202
2019	44,586
2020	54,206
2021	54,934
Thereafter	533,088
Total	785,426
Rent expense	50,300	$ 47,900	$ 39,900
Proceeds from sublease tenants	1,300	$ 3,600	$ 3,400
Letters of credit for real estate leases	$ 6,800

Commitments and Contingencies - Purchase Commitments (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Bandwidth and Co-location Commitments
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	$ 105,451
2018	13,799
2019	6,368
2020	386
2021	193
Thereafter	0
Total	126,197
Purchase Order Commitments
Unrecorded Unconditional Purchase Obligation [Line Items]
2017	137,642
2018	10,522
2019	1,827
2020	320
2021	320
Thereafter	0
Total	$ 150,631

Commitments and Contingencies - Narrative (Details)	1 Months Ended			12 Months Ended
Commitments and Contingencies - Narrative (Details)	Jul. 31, 2016 USD ($) installment	Jun. 30, 2016 USD ($)	Nov. 30, 2015 patent company	Dec. 31, 2016 USD ($)
Gain and Loss Contingencies [Line Items]
Loss in period		$ 700,000
Patent Infringement Case Against Limelight
Gain and Loss Contingencies [Line Items]
Settlement amount	$ 54,000,000
Number of installments in settlement \| installment	12
Settlement payment term	3 years
Proceeds from settlements				$ 9,000,000
Litigation settlement interest				400,000
Patent Infringement Case Against Limelight \| Pending Litigation
Gain and Loss Contingencies [Line Items]
Number of patents allegedly infringed upon \| patent			5
Patent Infringement Case Against Company and XO \| Pending Litigation
Gain and Loss Contingencies [Line Items]
Number of companies in case \| company			2
Number of patents allegedly infringed upon \| patent			6
Provision for loss				$ 0

Convertible Senior Notes - Narrative (Details) $ / shares in Units, shares in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2014 USD ($) d $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Debt issued	$ 690,000,000	$ 690,000,000	$ 690,000,000
Conversion rate (in shares)	11.1651
Principal amount per conversion	$ 1,000
Conversion price (in dollars per share) \| $ / shares	$ 89.56
Threshold trading days exceeding price \| d	20
Threshold consecutive trading days exceeding price	30 days
Threshold greater than percentage of stock price trigger	130.00%
Threshold trading days not exceeding price	5 days
Threshold consecutive trading days not exceeding price	5 days
Threshold less than percentage of stock price trigger	98.00%
Potential conversion shares of convertible debt (in shares) \| shares	7.7
Fair value of convertible senior notes		$ 721,400,000
Closing stock price (in dollars per share) \| $ / shares		$ 66.68
Repurchases of common stock	$ 62,000,000	$ 373,794,000	302,606,000	$ 268,647,000
Payments for purchase of convertible note hedge and warrant transactions	23,300,000
Payments for note hedge transactions	$ 101,300,000	0	0	101,292,000
Note hedge shares outstanding (in shares) \| shares	7.7
Warrants outstanding (in shares) \| shares	7.7
Warrant strike price (in dollars per share) \| $ / shares	$ 104.49
Proceeds from sale of warrants	$ 78,000,000	$ 0	$ 0	$ 77,970,000
Effective interest rate	3.20%

Convertible Senior Notes - Schedule of Convertible Senior Notes (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2014
Liability component:
Principal	$ 690,000,000	$ 690,000,000	$ 690,000,000
Less: debt discount and issuance costs, net of amortization	(49,913,000)	(71,953,000)
Net carrying amount	640,087,000	618,047,000
Convertible senior notes
Liability component:
Equity component:	$ 101,276,000	$ 101,276,000

Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Amortization of debt discount and issuance costs	$ 22,040	$ 21,280
Capitalization of interest expense	(3,402)	(2,755)
Total interest expense	$ 18,638	$ 18,525	$ 15,463

Stockholders' Equity - Narrative (Details) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 29, 2016	Oct. 31, 2013
Class of Stock [Line Items]
Amount of common stock repurchases authorized				$ 1,000,000,000.0	$ 750,000,000.0
Value of shares repurchased during period	$ 373,794,000	$ 302,606,000	$ 268,647,000
Remaining amount available for future purchases of shares under approved repurchase program.	$ 694,500,000
Common Stock
Class of Stock [Line Items]
Repurchases of common stock (in shares)	7.0	4.5	4.6
Value of shares repurchased during period	$ 373,800,000	$ 302,600,000	$ 268,600,000

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of January 1, 2016	$ 3,120,878	$ 2,945,335	$ 2,629,431
Other comprehensive loss	(14,769)	(23,842)	(15,520)
Balance as of December 31, 2016	3,224,370	3,120,878	2,945,335
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of January 1, 2016	(41,453)	(17,611)	(2,091)
Other comprehensive loss	(14,769)
Balance as of December 31, 2016	(56,222)	(41,453)	$ (17,611)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of January 1, 2016	(44,936)
Other comprehensive loss	(14,081)
Balance as of December 31, 2016	(59,017)	(44,936)
Net Unrealized Gains (Losses) on Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of January 1, 2016	3,483
Other comprehensive loss	(688)
Balance as of December 31, 2016	$ 2,795	$ 3,483

Employee Benefit Plan - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation Related Costs [Abstract]
Contributions by employer	$ 13.7	$ 13.1	$ 16.6

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax unrecognized compensation cost	$ 259.5
Weighted average period for recognizing compensation cost (in years)	2 years
Closing stock price (in dollars per share)	$ 66.68
In the money options exercisable (in shares)	800,000
Option granted (in shares)	0	0
Capitalized Internal Use Software
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional stock based compensation	$ 13.8	$ 12.7	$ 10.3
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Weighted average fair value of stock options granted (in dollars per share)			$ 49.67
Total pre-tax intrinsic value of options exercised	$ 18.3	53.6	$ 45.8
Total fair value of vested options	$ 6.5	$ 10.3	$ 16.9
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of equity instruments other than options granted (in dollars per share)	$ 14.54	$ 15.63	$ 12.64
Deferred Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of equity instruments other than options granted (in dollars per share)	$ 50.72
Each DSU receives this number of shares of common stock upon vesting (in whole numbers)	1
Holder elect to defer vested shares period, minimum (in years)	1 year
Holder elect to defer vested shares period, maximum (in years)	10 years
The amount typically vested by anniversary grant date (percentage)	100.00%
Number of years from date of grant DSUs are fully vested (in years)		2 years
Director's minimum period of service before vesting accelerates (in years)	1 year
Total pre-tax intrinsic value end of year	$ 1.4	$ 10.7	$ 1.4
Total fair value of vested and distributed	$ 1.6	$ 4.9	0.8
Unvested deferred stock units (in shares)	46,000
Aggregate intrinsic value	$ 3.1
Weighted average contractual remaining life (in years)	4 months 24 days
Granted (in shares)	46,000
Deferred Stock Units \| First Anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		50.00%
Deferred Stock Units \| Remaining After First Anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		50.00%
Deferred Stock Units \| Equal Installments After First Anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		12.50%
Deferred Stock Units \| Director Vesting Acceleration
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	100.00%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of equity instruments other than options granted (in dollars per share)	$ 56.40
Total pre-tax intrinsic value end of year	$ 128.5	$ 153.6	145.6
Total fair value of vested and distributed	140.4	$ 105.3	$ 86.9
Aggregate intrinsic value	$ 380.7
Weighted average contractual remaining life (in years)	2 years
Each RSU receives this number of shares of common stock upon vesting (in shares)	1
Granted (in shares)	4,116,000
Forfeited (in shares)	527,000
Restricted stock unit vesting provision, minimum (in years)	3 years
Restricted stock unit vesting provision, maximum (in years)	4 years
Number of equity instruments other than options unvested (in shares)	5,700,000
2009 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for grant (in shares)	3,800,000
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock approved for issuance under plan (in shares)	11,000,000.0
Common stock available for grant (in shares)	6,600,000
1999 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum amount of shares available for issuance (in shares)	1,500,000.0
Aggregate amount of shares available, maximum (in shares)	20,000,000.0
Discount on fair market value for purchase of stock (in percentage)	15.00%
Share purchase interval term (in months)	6 months
Issuance of common stock under employee stock purchase plan (in shares)	900,000	700,000	700,000
Weighted average purchase price (in dollars per share)	$ 46.23	$ 52.05	$ 41.76
Total cash proceeds from shares purchased	$ 39.9	$ 34.8	$ 29.3
Amount withheld from employees for future purchases	$ 5.1

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 144,506	$ 126,677	$ 111,996
Provision for income taxes	(49,014)	(49,033)	(39,182)
Total stock-based compensation, net of taxes	95,492	77,644	72,814
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	18,287	14,145	11,934
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	29,739	23,927	19,341
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	55,407	53,542	47,570
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 41,073	$ 35,063	$ 33,151

Stock-Based Compensation - Schedule of Stock Options Granted Black Scholes (Details)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	4 years 5 months
Risk-free interest rate	0.80%
Expected volatility	40.40%
Dividend yield	0.00%

Stock-Based Compensation - Schedule of Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			4 years 5 months
Risk-free interest rate			0.80%
Expected volatility			40.40%
Dividend yield			0.00%
Market-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years
Risk-free interest rate	0.80%
Expected volatility	34.30%
Average volatility of peer-company share price	27.60%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months
Risk-free interest rate	0.50%	0.20%	0.10%
Expected volatility	36.20%	28.00%	33.50%
Dividend yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Schedule of Summary of Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Shares (in thousands)
Outstanding at January 1, 2016 (in shares) \| shares	1,524
Exercised (in shares) \| shares	(643)
Forfeited (in shares) \| shares	(7)
Outstanding at December 31, 2016 (in shares) \| shares	874
Exercisable at December 31, 2016 (in shares) \| shares	829
Vested or expected to vest December 31, 2016 (in shares) \| shares	870
Weighted Average Exercise Price
Outstanding at January 1, 2016 (in dollars per share) \| $ / shares	$ 32.39
Exercised (in dollars per share) \| $ / shares	28.17
Forfeited (in dollars per share) \| $ / shares	29.69
Outstanding at December 31, 2016 (in dollars per share) \| $ / shares	35.51
Exercisable at December 31, 2016 (in dollars per share) \| $ / shares	35.58
Vested or expected to vest December 31, 2016 (in dollars per share) \| $ / shares	$ 35.52
Weighted Average Remaining Contractual Term & Aggregate Intrinsic Value
Outstanding at December 31, 2016	2 years 4 months 10 days
Exercisable at December 31, 2016	2 years 2 months 27 days
Vested or expected to vest December 31, 2016	2 years 4 months 6 days
Outstanding at December 31, 2016 \| $	$ 27,261
Exercisable at December 31, 2016 \| $	25,781
Vested or expected to vest December 31, 2016 \| $	$ 27,123

Stock-Based Compensation - Schedule of Restricted Stock Units by Type (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total restricted stock units vesting conditions granted (in shares)	4,116
Service-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units vesting conditions granted (in shares)	3,873
Market-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted with performance based vesting (in shares)	127
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted with performance based vesting (in shares)	116

Stock-Based Compensation - Schedule of Deferred Stock Units Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Deferred Stock Units
Units (in thousands)
Outstanding at January 1, 2016 (in shares) \| shares	146
Granted (in shares) \| shares	46
Vested and distributed (in shares) \| shares	(28)
Outstanding at December 31, 2016 (in shares) \| shares	164
Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016 (in dollars per share) \| $ / shares	$ 45.42
Granted (in dollars per share) \| $ / shares	50.72
Vested and distributed (in dollars per share) \| $ / shares	57.24
Outstanding at December 31, 2016 (in dollars per share) \| $ / shares	$ 44.90
Restricted Stock Units (RSUs)
Units (in thousands)
Outstanding at January 1, 2016 (in shares) \| shares	4,495
Granted (in shares) \| shares	4,116
Vested and distributed (in shares) \| shares	(2,374)
Forfeited (in shares) \| shares	(527)
Outstanding at December 31, 2016 (in shares) \| shares	5,710
Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016 (in dollars per share) \| $ / shares	$ 62.20
Granted (in dollars per share) \| $ / shares	56.40
Vested and distributed (in dollars per share) \| $ / shares	59.13
Forfeited (in dollars per share) \| $ / shares	59.68
Outstanding at December 31, 2016 (in dollars per share) \| $ / shares	$ 59.51

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Deferred benefit on intercompany sales	$ 9,100	$ 15,500	$ 24,300
Deferred tax assets, valuation allowance	430	1,217
Undistributed foreign earnings	470,400
Deferred income tax liability on undistributed foreign earnings	89,400
Unrecognized tax benefits including accrued interest and penalties	77,100	72,300	41,100
Unrecognized tax benefits, income tax penalties and interest accrued	13,700	10,000	7,700
Income tax interest and penalties expense	3,900	$ 2,200	$ 1,800
Unrecognized tax benefits that may be recognized	$ 15,800

Income Taxes - Components of Income Tax Schedule (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S.	$ 273,176	$ 233,247	$ 408,391
Foreign	186,270	223,377	71,385
Income before provision for income taxes	$ 459,446	$ 456,624	$ 479,776

Income Taxes - Provision for Income Tax Schedule (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax provision (benefit):
Federal	$ 89,816	$ 70,298	$ 153,471
State	6,238	(1,750)	4,978
Foreign	39,952	62,572	13,259
Deferred tax provision (benefit):
Federal	4,265	23,381	(13,073)
State	(86)	(742)	(15,220)
Foreign	3,916	(18,536)	2,442
Change in valuation allowance	(787)	(5)	(29)
Total	$ 143,314	$ 135,218	$ 145,828

Income Taxes - Schedule of Difference Between Effective and Statutory (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S. federal income tax rate	35.00%	35.00%	35.00%
State taxes	2.00%	1.70%	2.30%
Nondeductible stock-based compensation	2.30%	1.90%	1.40%
U.S. federal, state and foreign research and development credits	(3.30%)	(4.10%)	(3.20%)
Foreign earnings	(3.40%)	(4.60%)	(1.90%)
Domestic production activities deduction	(1.70%)	(1.20%)	(2.20%)
State software development activities benefit	(0.00%)	(0.00%)	(2.40%)
Other	0.30%	0.90%	1.40%
Effective income tax rate	31.20%	29.60%	30.40%

Income Taxes - Schedule of Deferred Tax and Related Valuation Allowance (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Accrued bonus	$ 18,390	$ 13,161
Deferred revenue	10,055	11,334
Deferred rent	12,592	13,224
Stock-based compensation	32,030	31,705
Net operating losses	7,855	8,855
Unrealized losses	1,862	1,421
Tax credit carryforwards	23,629	22,918
License income	16,932	0
Other	7,048	5,989
Deferred tax assets	130,393	108,607
Depreciation and amortization	(10,470)	(10,848)
Acquired intangible assets	(44,788)	(37,923)
Internal-use software development costs capitalized	(77,375)	(66,807)
Deferred tax liabilities	(132,633)	(115,578)
Valuation allowance	(430)	(1,217)
Net deferred tax liabilities	$ (2,670)	$ (8,188)

Income Taxes - Schedule of NOL Carryforwards (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Federal and state research and development tax credit carryforwards	$ 41,500	$ 39,800
Domestic country
Operating Loss Carryforwards [Line Items]
NOL carryforwards	16,500	21,500
State and local jurisdiction
Operating Loss Carryforwards [Line Items]
NOL carryforwards	11,400	28,200
Foreign country
Operating Loss Carryforwards [Line Items]
NOL carryforwards	$ 0	$ 0

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 65,290	$ 33,320	$ 24,651
Gross increases — tax positions of prior periods	6,391	11,238	12,925
Gross increases — current-period tax positions	6,252	27,043	2,106
Gross decreases — tax positions of prior periods	(6,778)	(5,996)	(6,362)
Gross decreases — settlements	(2,038)	(315)	0
Balance at end of year	$ 69,117	$ 65,290	$ 33,320

Net Income per Share - Schedule of Components Used in Diluted and Basic Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income	$ 91,639	$ 76,000	$ 73,635	$ 74,858	$ 88,420	$ 88,040	$ 67,200	$ 77,746	$ 316,132	$ 321,406	$ 333,948
Denominator:
Shares used for basic net income per share (in shares)									174,917	178,391	178,279
Effect of dilutive securities:
Stock options (in shares)									384	794	1,221
RSUs and deferred stock units (in shares)									914	1,230	1,686
Convertible senior notes (in shares)									0	0	0
Warrants related to issuance of convertible senior notes (in shares)									0	0	0
Shares used for diluted net income per share (in shares)									176,215	180,415	181,186
Basic net income per share (in dollars per share)	$ 0.53	$ 0.44	$ 0.42	$ 0.42	$ 0.50	$ 0.49	$ 0.38	$ 0.44	$ 1.81	$ 1.80	$ 1.87
Diluted net income per share (in dollars per share)	$ 0.52	$ 0.43	$ 0.42	$ 0.42	$ 0.49	$ 0.49	$ 0.37	$ 0.43	$ 1.79	$ 1.78	$ 1.84

Net Income per Share - Schedule of Anti-Dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	18,418	17,097	17,166
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	58	22	402
Service-based RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	2,262	660	786
Performance-based RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	690	1,007	570
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	7,704	7,704	7,704
Warrants related to issuance of convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	7,704	7,704	7,704

Segment and Geographic Information - Narrative (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments \| segment									1
Property and equipment, net	$ 801,017				$ 753,180				$ 801,017	$ 753,180
Revenue	616,124	$ 584,065	$ 572,135	$ 567,725	579,159	$ 551,030	$ 540,723	$ 526,536	2,340,049	2,197,448	$ 1,963,874
United States
Segment Reporting Information [Line Items]
Property and equipment, net	297,800				298,900				297,800	298,900
Non-U.S.
Segment Reporting Information [Line Items]
Property and equipment, net	$ 231,800				$ 227,800				231,800	227,800
Revenue									$ 720,000	$ 593,000	$ 531,900
Sales \| Geographic Concentration Risk \| United States
Segment Reporting Information [Line Items]
Concentration risk percent (more than)										10.00%	10.00%
Sales \| Geographic Concentration Risk \| Non-U.S.
Segment Reporting Information [Line Items]
Concentration risk percent (more than)									10.00%

Quarterly Financial Results (unaudited) - Schedule of Quarterly Financial Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 616,124	$ 584,065	$ 572,135	$ 567,725	$ 579,159	$ 551,030	$ 540,723	$ 526,536	$ 2,340,049	$ 2,197,448	$ 1,963,874
Cost of revenue (exclusive of amortization of acquired intangible assets)	203,475	204,467	206,323	194,736	193,212	183,204	179,910	169,294	809,001	725,620	610,943
Net income	$ 91,639	$ 76,000	$ 73,635	$ 74,858	$ 88,420	$ 88,040	$ 67,200	$ 77,746	$ 316,132	$ 321,406	$ 333,948
Basic net income per share (in dollars per share)	$ 0.53	$ 0.44	$ 0.42	$ 0.42	$ 0.50	$ 0.49	$ 0.38	$ 0.44	$ 1.81	$ 1.80	$ 1.87
Diluted net income per share (in dollars per share)	$ 0.52	$ 0.43	$ 0.42	$ 0.42	$ 0.49	$ 0.49	$ 0.37	$ 0.43	$ 1.79	$ 1.78	$ 1.84