Akamai (AKAM) 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 24, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Entity Registrant Name	AKAMAI TECHNOLOGIES INC
Entity Central Index Key	1086222
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		178,833,747
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Public Float			$10,533.70

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$238,650	$333,891
Marketable securities	519,642	340,005
Accounts receivable, net of reserves of $9,023 and $3,703 at December 31, 2014 and 2013, respectively	329,578	271,988
Prepaid expenses and other current assets	128,981	62,096
Deferred income tax assets	45,704	21,734
Total current assets	1,262,555	1,029,714
Property and equipment, net	601,591	450,287
Marketable securities	869,992	573,026
Goodwill	1,051,294	757,368
Acquired intangible assets, net	132,412	77,429
Deferred income tax assets	1,955	2,325
Other assets	81,747	67,536
Total assets	4,001,546	2,957,685
Current liabilities:
Accounts payable	77,412	73,710
Accrued expenses	204,686	150,385
Deferred revenue	49,679	36,952
Other current liabilities	2,234	2,119
Total current liabilities	334,011	263,166
Deferred revenue	3,829	3,199
Deferred income tax liabilities	39,299	4,737
Convertible senior notes	604,851	0
Other liabilities	74,221	57,152
Total liabilities	1,056,211	328,254
Commitments and contingencies (Note 10)
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; 178,300,603 and 178,580,696 shares issued and outstanding at December 31, 2014 and 2013, respectively.	1,783	1,808
Additional paid-in capital	4,559,430	4,561,929
Accumulated other comprehensive loss	-17,611	-2,091
Accumulated deficit	-1,598,267	-1,932,215
Total stockholders’ equity	2,945,335	2,629,431
Total liabilities and stockholders’ equity	$4,001,546	$2,957,685

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Accounts receivable reserve (in dollars)	$9,023	$3,703
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	178,300,603	178,580,696
Common stock, shares outstanding	178,300,603	178,580,696

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenue	$1,963,874	$1,577,922	$1,373,947
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	610,943	511,087	529,900
Research and development	125,286	93,879	74,744
Sales and marketing	379,035	280,380	223,348
General and administrative	325,845	255,218	210,100
Amortization of acquired intangible assets	32,057	21,547	20,962
Restructuring charges	1,189	1,843	406
Total costs and operating expenses	1,474,355	1,163,954	1,059,460
Income from operations	489,519	413,968	314,487
Interest income	7,680	6,077	6,455
Interest expense	-15,463	0	0
Other (expense) income, net	-1,960	-491	649
Income before provision for income taxes	479,776	419,554	321,591
Provision for income taxes	145,828	126,067	117,602
Net income	$333,948	$293,487	$203,989
Net income per share:
Basic (in dollars per share)	$1.87	$1.65	$1.15
Diluted (in dollars per share)	$1.84	$1.61	$1.12
Shares used in per share calculations:
Basic (in shares)	178,279	178,196	177,900
Diluted (in shares)	181,186	181,783	181,749

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$333,948	$293,487	$203,989
Other comprehensive loss:
Foreign currency translation adjustments	-15,349	-4,361	-904
Change in unrealized gain on investments, net of income tax benefit (expense) of $689, $457 and $(404) for the years ended December 31, 2014, 2013 and 2012, respectively	-171	3,910	523
Other comprehensive loss	-15,520	-451	-381
Comprehensive income	$318,428	$293,036	$203,608

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Tax on change in unrealized gain on investments, net	$689	$457	($404)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$333,948	$293,487	$203,989
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	247,406	184,431	204,163
Stock-based compensation	111,996	95,884	90,585
Provision (benefit) for doubtful accounts	1,981	1,169	-316
Excess tax benefits from stock-based compensation	-32,238	-22,801	-23,015
(Benefit) provision for deferred income taxes	-25,880	27,343	-5,819
Amortization of debt discount and issuance costs	15,463	0	0
Non-cash portion of restructuring charges	0	781	0
(Gain) loss on disposal of property and equipment	-159	414	3
Loss on investments	443	0	0
Gain from divestiture of a business	0	-1,188	0
Change in fair value of contingent consideration	300	0	0
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	-58,397	-67,184	-2,108
Prepaid expenses and other current assets	-60,788	-3,842	6,357
Accounts payable and accrued expenses	94,698	40,533	58,672
Deferred revenue	7,725	11,495	4,552
Other current liabilities	-702	52	-3,278
Other non-current assets and liabilities	22,274	3,334	-3,765
Net cash provided by operating activities	658,070	563,908	530,020
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	-386,532	-30,657	-336,680
Purchases of property and equipment	-207,159	-187,964	-166,773
Capitalization of internal-use software development costs	-111,468	-72,109	-54,204
Purchases of short- and long-term marketable securities	-1,225,409	-494,885	-752,342
Proceeds from sales and redemptions of short- and long-term marketable securities	373,730	160,210	214,277
Proceeds from maturities of short- and long-term marketable securities	372,287	314,925	315,788
Proceeds from sale of property and equipment	1,371	827	12
Other non-current assets and liabilities	4,374	-3,455	812
Net cash used in by investing activities	-1,178,806	-313,108	-779,110
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes, net of issuance costs	678,735	0	0
Proceeds from the issuance of warrants related to convertible senior notes	77,970	0	0
Purchase of note hedge related to convertible senior notes	-101,292	0	0
Repayment of acquired debt and capital leases	-17,862	0	0
Payment of contingent consideration related to acquired business	-1,575	0	0
Proceeds related to the issuance of common stock under stock plans	87,109	63,707	45,114
Excess tax benefits from stock-based compensation	32,238	22,801	23,015
Employee taxes paid related to net share settlement of stock-based awards	-50,649	-41,332	-34,690
Repurchases of common stock	-268,647	-160,419	-141,468
Net cash provided by (used in) financing activities	436,027	-115,243	-108,029
Effects of exchange rate changes on cash and cash equivalents	-10,532	-3,655	-89
Net increase (decrease) in cash and cash equivalents	-95,241	131,902	-357,208
Cash and cash equivalents at beginning of year	333,891	201,989	559,197
Cash and cash equivalents at end of year	238,650	333,891	201,989
Supplemental disclosure of cash flow information:
Cash paid for income taxes	166,211	63,508	94,833
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	45,868	19,927	12,939
Capitalization of stock-based compensation	15,226	12,325	9,276
Convertible note receivable received for divestiture of a business	$0	$18,882	$0

Consolidated_Statements_Of_Sto

Consolidated Statements Of Stockholders' Equity (USD $)	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
In Thousands, except Share data, unless otherwise specified
Beginning balance at Dec. 31, 2011	$2,156,250	$1,959	$5,068,235	($482,994)	($1,259)	($2,429,691)
Beginning balance (in shares) at Dec. 31, 2011		177,504,624
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)		3,961,440
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	-6,853	49	-6,902
Issuance of common stock under employee stock purchase plan (in shares)		676,853
Issuance of common stock under employee stock purchase plan	16,823	7	16,816
Stock-based compensation	99,038		99,038
Tax benefits from stock-based award activity, net	17,533		17,533
Stock-based compensation from awards issued to non-employees for services rendered	823		823
Repurchases of common stock (in shares)		-4,360,103
Repurchases of common stock	-141,468			-141,468
Net income	203,989					203,989
Foreign currency translation adjustments	-904				-904
Change in unrealized gain on investments, net of tax	523				523
Ending balance at Dec. 31, 2012	2,345,754	2,015	5,195,543	-624,462	-1,640	-2,225,702
Ending balance (in shares) at Dec. 31, 2012		177,782,814
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)		4,050,525
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	-168	50	-218
Issuance of common stock under employee stock purchase plan (in shares)		644,639
Issuance of common stock under employee stock purchase plan	22,092	6	22,086
Stock-based compensation	107,882		107,882
Tax benefits from stock-based award activity, net	20,926		20,926
Stock-based compensation from awards issued to non-employees for services rendered	327		327
Repurchases of common stock (in shares)		-3,897,282
Repurchases of common stock	-160,418			-160,418
Treasury stock retirement	0	-263	-784,617	784,880
Net income	293,487					293,487
Foreign currency translation adjustments	-4,361				-4,361
Change in unrealized gain on investments, net of tax	3,910				3,910
Ending balance at Dec. 31, 2013	2,629,431	1,808	4,561,929	0	-2,091	-1,932,215
Ending balance (in shares) at Dec. 31, 2013		178,580,696
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 at Dec. 31, 2014	$2,945,335	$1,783	$4,559,430	$0	($17,611)	($1,598,267)
Ending balance (in shares) at Dec. 31, 2014		178,300,603

Nature_of_Business_and_Basis_o

Nature of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2014
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 online content and business applications. The Company's globally distributed platform comprises more than 170,000 servers in approximately 1,300 networks in over 100 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 online content and business applications.
	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_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
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, 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 more than three months at the date of purchase and less than one year from the date of the balance sheets 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 sheets.
	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 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 operations. 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 of, and business outlook for 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 operations. 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, 2014, 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, 2014, 2013 and 2012, no customer accounted for more than 10% of total revenue. As of December 31, 2014, no customers had an accounts receivable balance greater than 10% of total accounts receivable. As of December 31, 2013, one customer had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2014, 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.
	Effective January 1, 2013, the Company increased the expected average useful lives of its network assets, primarily servers, from three to four years to reflect software and hardware related initiatives to manage its global network more efficiently. This change was recorded prospectively and decreased depreciation expense on network assets for the years ended December 31, 2014 and 2013 by approximately $21.1 million and $45.7 million, respectively, and increased net income for the years ended December 31, 2014 and 2013 by approximately $15.5 million and $33.6 million, respectively. The change also increased both basic and diluted net income per share for the year ended December 31, 2014 by $0.09; and for the year ended December 31, 2013, by $0.19 and $0.18, respectively.
	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, 2014, 2013 and 2012, 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, 2014, 2013 and 2012.
	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. The Company did not have any impairments during the years ended December 31, 2014, 2013 and 2012.
	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 all solution unit pricing 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 a reseller channel. 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 network operation, build-out and support and services delivery; 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 two 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 discounted 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 during the application development stage, as well as interest expense related to the Company's senior convertible notes. Capitalization begins when the planning stage is complete and the Company commits resources to the software project. Capitalization ceases when the software has been tested and is ready for its intended use. The Company amortizes completed internal-use software to cost of revenue over its estimated useful life. Costs incurred during the planning, training and post-implementation stages of the software development life-cycle are expensed as incurred.
	Advertising Expense
	The Company recognizes advertising expense as incurred. The Company recognized total advertising expense of $2.7 million for each of the years ended December 31, 2014 and 2013, and $2.8 million for the year ended December 31, 2012.
	Accounting for Stock-Based Compensation
	The Company recognizes compensation costs for all stock-based payment awards made to employees and directors 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 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 operation.
	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 (expense) income, 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 (expense) income, net. As of December 31, 2014 and 2013, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2014, 2013 and 2012 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 to determine the amount of tax benefit to be recognized. 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.
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step analysis of transactions to determine when and how revenue is recognized.  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. This guidance will be effective for the Company on January 1, 2017 and may be applied retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption.  The Company is evaluating the potential impact of adopting this new accounting guidance.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements
	The following is a summary of available-for-sale marketable securities held as of December 31, 2014 and 2013 (in thousands):
					Gross Unrealized						Aggregate			Classification on Balance Sheet
		Amortized Cost									Fair Value			Short-Term		Long-Term
														Marketable		Marketable
	As of December 31, 2014				Gains			Losses						Securities		Securities
	Certificates of deposit	$	39		$	—		$	—		$	39		$	—	$	39
	Commercial paper	10,487			—			(2		)	10,485			10,485		—
	Corporate bonds	1,077,387			454			(2,132		)	1,075,709			424,777		650,932
	U.S. government agency obligations	303,808			20			(427		)	303,401			84,380		219,021
		$	1,391,721		$	474		$	(2,561	)	$	1,389,634		$	519,642	$	869,992
	As of December 31, 2013
	Certificates of deposit	$	222		$	—		$	—		$	222		$	173	$	49
	Corporate bonds	736,945			1,197			(281		)	737,861			278,318		459,543
	U.S. government agency obligations	174,982			51			(85		)	174,948			61,514		113,434
		$	912,149		$	1,248		$	(366	)	$	913,031		$	340,005	$	573,026
	Unrealized gains and unrealized temporary losses on investments classified as available-for-sale are included within accumulated other comprehensive loss. Upon realization, those amounts are reclassified from accumulated other comprehensive loss to interest income in the consolidated statements of operations. The Company does not believe any unrealized losses represent other than temporary impairments based on the evaluation of available evidence. As of December 31, 2014, the Company did not hold any investment-related assets that had been in a continuous loss position for more than 12 months.
	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, 2014 and 2013 (in thousands):
		Total Fair Value			Fair Value Measurements at Reporting Date Using
					Level 1			Level 2			Level 3
	As of December 31, 2014
	Cash Equivalents and Marketable Securities:
	Money market funds	$	501		$	501		$	—		$	—
	Certificates of deposit	39			39			—			—
	Commercial paper	10,485			—			10,485			—
	Corporate bonds	1,075,709			—			1,075,709			—
	U.S. government agency obligations	303,401			—			303,401			—
		$	1,390,135		$	540		$	1,389,595		$	—
	Other Liabilities:
	Contingent consideration obligation related to Velocius acquisition	$	(900	)	$	—		$	—		$	(900	)
	As of December 31, 2013
	Cash Equivalents and Marketable Securities:
	Money market funds	$	40,482		$	40,482		$	—		$	—
	Certificates of deposit	3,418			3,418			—			—
	Commercial paper	29,999			—			29,999			—
	Corporate bonds	737,861			—			737,861			—
	U.S. government agency obligations	174,948			—			174,948			—
		$	986,708		$	43,900		$	942,808		$	—
	Other Assets:
	Note receivable	$	22,879		$	—		$	—		$	22,879
	Other Liabilities:
	Contingent consideration obligation related to Velocius acquisition	$	(2,600	)	$	—		$	—		$	(2,600	)
	As of December 31, 2014 and 2013, the Company grouped money market funds and certificates of deposit using a Level 1 valuation because market prices for such investments are readily available in active markets. As of December 31, 2014 and 2013, 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 and liabilities between Level 1 and Level 2 of the fair value measurement hierarchy during the years ended December 31, 2014 and 2013.
	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 the fair value of a Level 3 asset held by the Company and consisting of a $25.0 million face value convertible note receivable, was primarily an income approach, where the expected weighted average future cash flows were discounted back to present value. The significant unobservable inputs used in the fair value measurement of the convertible note receivable were the probability of conversion to equity and the fair value of equity into which the note was convertible. In the second quarter of 2014, the note was amended. Under the terms of the amendment, the note became convertible into shares of preferred stock of the issuer valued at $12.5 million at the time of conversion; the remaining $12.5 million was paid in cash in the second and third quarters of 2014.
	The valuation technique used to measure fair value of the Company's Level 3 liability, which consists of contingent consideration related to the acquisition of Velocius Networks, Inc. ("Velocius") (Note 8), is primarily an income approach. The significant unobservable input used in the fair value measurement of the Velocius contingent consideration is the likelihood of achieving development milestones to integrate the acquired technology into the Company's technology. During the third quarter of 2014, the first of two milestones was achieved and a portion of the contingent consideration was paid. The remaining milestone is payable in the third quarter of 2015, if achieved.
	Increases or decreases in the underlying assumptions used to value the Company's Level 3 asset and liability, respectively, could increase or decrease the fair value estimates recorded in the consolidated balance sheets.
	Contractual maturities of the Company’s available-for-sale marketable securities held as of December 31, 2014 and 2013 were as follows (in thousands):
		December 31, 2014			December 31, 2013
	Due in 1 year or less	$	519,642		$	340,005
	Due after 1 year through 5 years	869,992			573,026
		$	1,389,634		$	913,031
	The following table reflects the activity for the Company’s major classes of assets and liabilities measured at fair value using Level 3 inputs for the years ended December 31, 2014 and 2013 (in thousands):
		Other Assets:			Other Liabilities:
		Note Receivable			Contingent Consideration Obligation
	Balance, January 1, 2013	$	—		$	(1,200	)
	Fair value adjustment to contingent consideration for acquisition of Verivue included in general and administrative expense	—			1,200
	Contingent consideration obligation related to Velocius acquisition	—			(2,600		)
	Convertible note receivable from divestiture of a business	18,882			—
	Unrealized gain on convertible note receivable included in other comprehensive income	3,997			—
	Balance, December 31, 2013	$	22,879		$	(2,600	)
	Fair value adjustment to Velocius contingent consideration included in general and administrative expense	—			(300		)
	Achievement of first milestone related to Velocius contingent consideration	—			2,000
	Unrealized gain on convertible note receivable included in other comprehensive income	2,121			—
Amendment of the convertible note receivable for preferred stock of the issuer and cash	(25,000		)	—
Balance, December 31, 2014	$	—		$	(900	)

Accounts_Receivable

Accounts Receivable	12 Months Ended
	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Accounts Receivable	Accounts Receivable
	Net accounts receivable consisted of the following as of December 31, 2014 and 2013 (in thousands):
		December 31, 2014			December 31, 2013
	Trade accounts receivable	$	222,531		$	175,391
	Unbilled accounts receivable	116,070			100,300
	Gross accounts receivable	338,601			275,691
	Allowance for doubtful accounts	(1,033		)	(708		)
	Reserve for cash-basis customers	(7,990		)	(2,995		)
	Total accounts receivable reserves	(9,023		)	(3,703		)
	Accounts receivable, net	$	329,578		$	271,988
	A summary of activity in the accounts receivable reserves for the years ended December 31, 2014, 2013 and 2012, is as follows (in thousands):
		2014			2013			2012
	Beginning balance	$	3,703		$	3,807		$	4,555
	Charges to income from operations	32,293			17,900			15,599
	Collections from cash basis customers and write-offs	(26,973		)	(18,004		)	(16,347		)
	Ending balance	$	9,023		$	3,703		$	3,807
	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.

Prepaid_Expenses_and_Other_Cur

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid Expense and Other Current Assets
	Prepaid expenses and other current assets consisted of the following as of December 31, 2014 and 2013 (in thousands):
		31-Dec-14		31-Dec-13
	Prepaid income taxes	$	44,631	$	3,249
	Other prepaid expenses	37,669		29,498
	Other current assets	46,681		29,349
	Total	$	128,981	$	62,096

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment
	Property and equipment consisted of the following as of December 31, 2014 and 2013 (dollars in thousands):
		31-Dec-14			31-Dec-13			Estimated Useful Life in Years
	Computer and networking equipment	$	850,533		$	737,957		4-Mar
	Purchased software	46,537			40,237			3
	Furniture and fixtures	27,923			20,838			5
	Office equipment	14,035			10,353			3
	Leasehold improvements	92,544			64,471			12-Feb
	Internal-use software	448,777			340,421			7-Feb
	Property and equipment, gross	1,480,349			1,214,277
	Accumulated depreciation and amortization	(878,758		)	(763,990		)
	Property and equipment, net	$	601,591		$	450,287
	Depreciation and amortization expense on property and equipment and capitalized internal-use software for the years ended December 31, 2014, 2013 and 2012 was $215.3 million, $162.9 million and $183.2 million, respectively. During the years ended December 31, 2014, 2013 and 2012, the Company capitalized $15.2 million, $12.3 million and $9.3 million, respectively, of stock-based compensation related to employees who developed and enhanced internal-use software applications.
	During the years ended December 31, 2014 and 2013, the Company wrote off $100.1 million and $68.5 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 were substantially depreciated and amortized.

Goodwill_and_Acquired_Intangib

Goodwill and Acquired Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Intangible Assets	Goodwill and Acquired Intangible Assets
	The changes in the carrying amount of goodwill for the years ended December 31, 2014 and 2013 were as follows (in thousands):
		2014		2013
	Beginning balance	$	757,368	$	723,701
	Additions	293,926		35,606
	Disposals	—		(1,939		)
	Ending balance	$	1,051,294	$	757,368
	The addition to goodwill during the year ended December 31, 2014 was related to the acquisition of Prolexic Technologies, Inc. ("Prolexic"). The additions to goodwill during the year ended December 31, 2013 were related to the acquisitions of strategic network assets from AT&T Services, Inc. ("AT&T") and of Velocius. The disposal of goodwill during the year ended December 31, 2013 was related to the sale of the Company's Advertising Decision Solutions ("ADS") business.
	Acquired intangible assets that are subject to amortization consisted of the following as of December 31, 2014 and 2013 (in thousands):
		December 31, 2014							December 31, 2013
		Gross		Accumulated			Net		Gross		Accumulated			Net
		Carrying		Amortization			Carrying		Carrying		Amortization			Carrying
		Amount					Amount		Amount					Amount
	Completed technologies	$	88,331	$	(45,537	)	$	42,794	$	65,631	$	(35,476	)	$	30,155
	Customer relationships	173,600		(91,160		)	82,440		115,100		(75,563		)	39,537
	Non-compete agreements	8,890		(4,224		)	4,666		7,950		(2,623		)	5,327
	Trademarks and trade names	3,700		(1,188		)	2,512		3,400		(990		)	2,410
	Acquired license rights	490		(490		)	—		490		(490		)	—
	Total	$	275,011	$	(142,599	)	$	132,412	$	192,571	$	(115,142	)	$	77,429
	Aggregate amortization expense of acquired intangible assets for the years ended December 31, 2014, 2013 and 2012 was $32.1 million, $21.5 million and $21.0 million, respectively. Based on intangible assets held as of December 31, 2014, amortization expense is expected to be approximately $26.8 million, $25.2 million, $23.1 million, $16.2 million and $12.6 million for the years ending December 31, 2015, 2016, 2017, 2018 and 2019, respectively.

Business_Acquisitions_and_Dive

Business Acquisitions and Divestitures	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Acquisitions and Divestitures	Business Acquisitions and Divestitures
	Acquisition-related costs were $4.2 million, $3.1 million and $5.8 million during the years ended December 31, 2014, 2013 and 2012, 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 2014, 2013 and 2012 have not been presented because the effects of the acquisitions, individually or in the aggregate, are not material to the Company's consolidated financial results. Revenue and earnings since the date of the acquisitions included in the Company's consolidated statements of operations are also not included because they are not material.
	2014 Acquisitions
	Prolexic Acquisition
	On February 18, 2014, the Company acquired all of the outstanding capital stock of Prolexic in exchange for $392.1 million in cash and the assumption of unvested stock options. The goal of acquiring Prolexic was to provide 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 expected cost synergies 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
	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.
	2013 Acquisitions
	Velocius Acquisition
	On November 8, 2013, the Company acquired Velocius in exchange for $4.3 million in cash. In addition, the Company recorded a liability of $2.6 million for contingent consideration related to expected achievement of post-closing milestones. The maximum potential payout of the contingent consideration is $3.0 million. As of December 31, 2014, the first of two milestones was achieved and the remaining contingent consideration has a fair value of $0.9 million.
	The Company acquired Velocius with a goal of complementing its hybrid cloud optimization strategy for optimizing IP application traffic across the Internet for remote and branch-end users. The Company allocated $5.4 million of the cost of the acquisition to goodwill and $2.5 million to acquired intangible assets. The allocation of the purchase price was finalized in the first quarter of 2014. The total weighted average useful life of the intangible assets acquired from Velocius is 7.9 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. The total amount of goodwill related to the acquisition of Velocius expected to be deducted for tax purposes is $0.3 million.
	Strategic Network Transaction
	On November 30, 2012, the Company entered into a strategic alliance with AT&T. Under the agreement, AT&T became a reseller of the Company's services and the Company acquired certain assets and contracted to purchase bandwidth, co-location and related services from AT&T. The Company entered into the agreement with a goal of expanding its content delivery network customer base and developing a relationship with AT&T as a bandwidth and co-location service provider. The transaction meets the definition of a business combination, and it was determined that the Company obtained control of the acquired assets in July 2013. The total consideration is $55.0 million, of which $27.5 million was paid during the third quarter of 2013 and $27.5 million was paid during the first quarter of 2014.
	The Company allocated $30.2 million of the consideration to goodwill and $16.1 million to acquired intangible assets. The allocation of the purchase price was finalized in the fourth quarter of 2013. The weighted average useful life of the intangible assets acquired is 9.8 years. The value of the goodwill acquired can be attributed to expected synergies between AT&T and the Company related to future customer expansion and cost reductions. The total amount of goodwill expected to be deducted for tax purposes is $30.2 million.
	2012 Acquisitions
	Verivue Acquisition
	On December 4, 2012, the Company acquired all of the outstanding common and preferred stock of Verivue, Inc. ("Verivue") in exchange for $30.9 million in cash. In addition, the Company recorded a liability of $1.2 million for contingent consideration related to expected achievement of post-closing milestones. The Company acquired Verivue with a goal of complementing its network operator solutions and accelerating time to market in providing a comprehensive, licensed content delivery network solution for network operators. The Company allocated $14.9 million of the cost of the acquisition to goodwill and $7.5 million to acquired intangible assets. The purchase price was finalized in the third quarter of 2013. The Company recorded a reduction of $5.8 million to goodwill upon the finalization of measurement period adjustments related to deferred tax assets and liabilities in the third quarter of 2013 and revised prior period balances to reflect the change.
	The total weighted average useful life of the intangible assets acquired from Verivue is 6.4 years. The value of the goodwill from the acquisition can be attributed to a number of business factors, including a trained technical workforce in place in the United States and expected cost synergies. The total amount of goodwill related to the acquisition of Verivue expected to be deducted for tax purposes is $3.0 million. As of March 31, 2013, the Company determined the agreed upon post-closing milestones were not expected to be achieved and therefore expensed the $1.2 million contingent consideration recorded at December 31, 2012 as general and administrative expense in the consolidated statement of operations. As of December 31, 2014, the milestones were not achieved.
	FastSoft Acquisition
	On September 13, 2012, the Company acquired all of the outstanding common and preferred stock of FastSoft, Inc. ("FastSoft") in exchange for $14.4 million in cash. The Company acquired FastSoft with a goal of complementing the Company's Media Delivery Solutions with technology for optimizing the throughput of video and other digital content across IP networks. The Company allocated $7.1 million of the cost of the acquisition to goodwill and $3.7 million to acquired intangible assets. The allocation of the purchase price was finalized in the third quarter of 2013. The Company recorded a reduction of $1.8 million to goodwill upon the finalization of measurement period adjustments related to deferred tax assets and liabilities in the third quarter of 2013, and revised prior period balances to reflect the change.
	The total weighted average useful life of the intangible assets acquired from FastSoft is 9.0 years. The value of the goodwill from the acquisition can be attributed to a number of business factors including a trained technical workforce in place in the U.S and cost synergies. The total amount of goodwill related to the acquisition of FastSoft expected to be deducted for tax purposes is $1.7 million.
	Cotendo Acquisition
	On March 6, 2012, the Company acquired all of the outstanding equity, of Cotendo, Inc. ("Cotendo") in exchange for $278.9 million in cash and assumption of unvested stock options. The Company acquired Cotendo with the intention of increasing the Company’s pace of innovation in the areas of site acceleration and mobile optimization.
	The purchase price allocation was finalized in the third quarter of 2013, and at that time, the Company recorded a reduction of $7.8 million to goodwill upon the finalization of measurement period adjustments primarily related to deferred tax liabilities.
	The following table presents the final allocation of the purchase price of Cotendo (in thousands):
	Total purchase consideration	$	278,877
	Allocation of the purchase consideration:
	Current assets, including cash and cash equivalents of $6,405	$	6,751
	Trade receivables	2,920
	Property and equipment	5,812
	Indemnification assets	6,200
	Long-term assets	75
	Identifiable intangible assets	43,800
	Goodwill	233,828
	Deferred tax liabilities	(15,376		)
	Other liabilities assumed	(5,133		)
	Net assets acquired	$	278,877
	The value of the goodwill from the acquisition of Cotendo can be attributed to a number of business factors including potential sales opportunities to provide the Company's services to Cotendo customers; a trained technical workforce in place in the U.S. and Israel; a trained sales force; and cost synergies expected to be realized. The total amount of goodwill related to the acquisition of Cotendo expected to be deducted for tax purposes is $44.4 million.
	The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except for years):
	Gross				Weighted Average Useful Life (in years)
	Carrying
	Amount
Completed technology	$	24,100			5.8
Customer relationships	13,400				8.8
Non-compete agreements	3,900				6
Trademarks and trade names	2,400				9.8
Total	$	43,800
The total weighted average amortization period for the intangible assets acquired from Cotendo is 7.1 years. The intangible assets are being amortized based upon the pattern in which the economic benefits of the intangible assets are being utilized.
Blaze
On February 7, 2012, the Company acquired all of the outstanding common and preferred stock, including vested and unvested stock options, of Blaze, Inc. ("Blaze") in exchange for $19.3 million in cash and assumption of unvested stock options. The Company acquired Blaze with a goal of complementing the Company's site acceleration solutions with technology designed to optimize the speed at which a web page is rendered. The Company allocated $15.1 million of the cost of the acquisition to goodwill and $5.1 million to acquired intangible assets. The purchase price allocation was finalized during 2012. The total weighted average useful life of the intangible assets acquired from Blaze is 5.3 years. The value of the goodwill from this acquisition can be attributed to a number of business factors including a trained technical workforce in place in Canada and cost synergies expected to be realized. The total amount of goodwill related to the acquisition of Blaze expected to be deducted for tax purposes is $13.5 million.
Divestitures
ADS Divestiture
Consistent with its strategy to prioritize higher-margin businesses, the Company sold its ADS business to MediaMath, Inc. ("MediaMath") in exchange for a $25.0 million face value convertible note receivable (Note 3). The transaction closed during the first quarter of 2013. These operations were not material to the Company's annual net sales, net income or earnings per share, and no significant gains or losses were realized on the transaction. The accompanying consolidated financial statements for the year ended December 31, 2013 include the impact of approximately one month of ADS operations prior to the sale. All assets and liabilities used by the ADS operations have been excluded from the consolidated balance sheets. Simultaneously with the sale, the Company entered into a multi-year relationship agreement whereby MediaMath will have exclusive rights to leverage the Company's pixel-free technology for use within digital advertising and marketing applications.
During the second quarter of 2014, the convertible note receivable was amended. Under the terms of the amendment, the note became convertible into shares of preferred stock of the issuer valued at $12.5 million at the time of conversion and is included in other assets in the consolidated balance sheet as of December 31, 2014; the remaining $12.5 million was received in cash during the second and third quarters of 2014.

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2014
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accrued Expenses	Accrued Expenses
	Accrued expenses consisted of the following as of December 31, 2014 and 2013 (in thousands):
		31-Dec-14		31-Dec-13
	Payroll and other related benefits	$	125,938	$	90,093
	Bandwidth and co-location	28,459		20,991
	Property, use and other taxes	40,411		32,503
	Professional service fees	4,434		4,388
	Other	5,444		2,410
	Total	$	204,686	$	150,385

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Operating Lease Commitments
	The Company leases its facilities under non-cancelable operating leases. These operating leases expire at various dates through March 2024 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, 2014 were as follows (in thousands):
	2015	$	40,728
	2016	40,916
	2017	40,510
	2018	32,972
	2019	29,723
	Thereafter	38,412
	Total	$	223,261
	Rent expense for the years ended December 31, 2014, 2013 and 2012 was $39.9 million, $30.8 million and $23.5 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 $3.4 million, $1.9 million and $1.4 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	As of December 31, 2014, the Company had outstanding letters of credit in the amount of $8.3 million related to certain of its real estate leases. The letters of credit expire as the Company fulfills its operating lease obligations.
	Purchase Commitments
	As of December 31, 2014, the Company has 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, 2014, the Company had entered into purchase orders with various vendors. The minimum future commitments as of December 31, 2014 were as follows (in thousands):
		Bandwidth and Co-location Commitments		Purchase Order Commitments
	2015	$	119,081	$	115,014
	2016	20,028		5,708
	2017	10,313		2,470
	2018	365		795
	2019	92		—
	Thereafter	—		—
	Total	$	149,879	$	123,987
	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.
	The Company is conducting an internal investigation, with the assistance of outside counsel, relating to sales practices in a country outside the U.S. that represented less than 1% of the Company’s revenue in each of the years ended December 31, 2014, 2013 and 2012. The internal investigation includes a review of compliance with the requirements of the U.S. Foreign Corrupt Practices Act and other applicable laws and regulations by employees in that market.  In February 2015, the Company voluntarily contacted the U.S. Securities and Exchange Commission and Department of Justice to advise both agencies of this internal investigation. As of the filing of these financial statements, the Company cannot predict the outcome of this matter. No provision with respect to this matter has been made in the Company's consolidated financial statements.
	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 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 could limit the Company’s exposure.
	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 indemnifications 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

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Convertible Senior Notes	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;
	•	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 with the equity component of the Notes in stockholders’ equity.
	The Notes consist of the following components as of December 31, 2014 (in thousands):
		December 31, 2014
	Liability component:
	Principal	$	690,000
	Less: debt discount, net of amortization	(85,149		)
	Net carrying amount	$	604,851
	Equity component:	$	101,276
	The estimated fair value of the Notes at December 31, 2014 was $720.9 million. The fair value was determined based on data points other than quoted prices that are observable, either directly or indirectly, and has been classified as Level 2 within the fair value hierarchy. Based on the closing price of the Company's common stock of $62.96 on December 31, 2014, 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, concurrently 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 Company intends to use the remaining net proceeds for working capital, share repurchases and other general corporate purposes, as well as for potential acquisitions and other 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. 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, 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 warrants expire beginning in May 2019. 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 statement of operations related to the Notes for the year ended December 31, 2014 (in thousands):
		For the Year Ended December 31, 2014
	Amortization of debt discount	$	16,127
	Amortization of debt issuance costs	1,531
	Capitalization of interest expense	(2,195		)
	Total interest expense	$	15,463

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
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 16, 2013 through December 31, 2016. During the years ended December 31, 2014, 2013 and 2012, the Company repurchased 4.6 million, 3.9 million and 4.4 million shares, respectively, of its common stock for $268.6 million, $160.4 million and $141.5 million, respectively pursuant to the current repurchase program as well as prior ones approved by the Board of Directors. As of December 31, 2014, the Company had $433.6 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 December 31, 2014 and 2013. 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.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Loss	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, 2014 (in thousands):
		Foreign Currency Translation			Net Unrealized Gains (Losses) on Investments			Total
	Balance, beginning of year	$	(6,715	)	$	4,624		$	(2,091	)
	Other comprehensive loss	(15,349		)	(171		)	(15,520		)
	Balance, end of year	$	(22,064	)	$	4,453		$	(17,611	)
	The tax effect on accumulated unrealized gains on investments as of December 31, 2014 and 2013, was immaterial. Amounts reclassified from accumulated other comprehensive loss to net income were insignificant for the year ended December 31, 2014.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2014
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 $16.6 million, $11.1 million and $6.4 million of cash to the savings plan for the years ended December 31, 2014, 2013 and 2012, respectively, under a matching program.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
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 8.0 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. As of December 31, 2014, the Company had reserved approximately 10.2 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, 2014, 2013 and 2012, the Company issued 0.7 million, 0.6 million and 0.7 million shares under the 1999 ESPP, respectively, with a weighted average purchase price per share of $41.76, $34.26 and $24.76, respectively. Total cash proceeds from the purchase of shares under the 1999 ESPP in 2014, 2013 and 2012 were $29.3 million, $22.1 million and $16.8 million, respectively. As of December 31, 2014, approximately $3.0 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 operations for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	Cost of revenue	$	11,934			$	10,867			$	11,309
	Research and development expense	19,341				17,472				17,275
	Sales and marketing expense	47,570				39,290				34,322
	General and administrative expense	33,151				28,255				27,679
	Total stock-based compensation	111,996				95,884				90,585
	Provision for income taxes	(39,182		)		(34,829		)		(33,126		)
	Total stock-based compensation, net of taxes	$	72,814			$	61,055			$	57,459
	In addition to the amounts of stock-based compensation reported in the table above, the Company’s consolidated statements of operations for the years ended December 31, 2014, 2013 and 2012 also include stock-based compensation reflected as a component of amortization of capitalized internal-use software; such additional stock-based compensation was $10.3 million, $8.1 million and $7.7 million, respectively, before tax.
	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 grant-date fair values of the Company's stock option awards granted during the years ended December 31, 2014, 2013 and 2012 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		2014			2013			2012
	Expected term (in years)	4.4			4.5			4.2
	Risk-free interest rate	0.8	%		0.8	%		0.6	%
	Expected volatility	40.4	%		44.4	%		50.8	%
	Dividend yield	—	%		—	%		—	%
	For the years ended December 31, 2014, 2013 and 2012, the weighted average fair value of stock option awards granted was $49.67 per share, $14.17 per share and $25.20 per share, respectively.
	The grant-date fair values of the Company's ESPP awards granted during the years ended December 31, 2014, 2013 and 2012 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		2014			2013			2012
	Expected term (in years)	0.5			0.5			0.5
	Risk-free interest rate	0.1	%		0.1	%		0.1	%
	Expected volatility	33.5	%		42	%		51	%
	Dividend yield	—	%		—	%		—	%
	For the years ended December 31, 2014, 2013 and 2012, the weighted average fair value of ESPP awards granted was $12.64 per share, $11.34 per share and $8.71 per share, respectively.
	As of December 31, 2014, 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 $145.1 million. The expense is expected to be recognized through 2018 over a weighted average period of 1.2 years.
	Stock Options
	The following table summarizes stock option activity during the year ended December 31, 2014:
		Shares			Weighted Average Exercise Price				Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
		(in thousands)							(in years)		(in thousands)
	Outstanding at January 1, 2014	4,458			$	30.67
	Granted	352			12.73
	Exercised	(1,978	)		28.87
	Forfeited	(161	)		47.02
	Outstanding at December 31, 2014	2,671			$	28.65			3.48		$	168,706
	Exercisable at December 31, 2014	1,933			$	28.66			2.68		$	121,722
	Vested or expected to vest December 31, 2014	2,662			$	28.52			3.45		$	167,600
	The shares granted during 2014 and presented in the table above include 328,000 stock options assumed by the Company as a result of the acquisition of Prolexic.
	The total pre-tax intrinsic value of options exercised during the years ended December 31, 2014, 2013 and 2012 was $45.8 million, $47.2 million and $47.9 million, respectively. The total fair value of options vested for the years ended December 31, 2014, 2013 and 2012 was $16.9 million, $12.4 million and $16.6 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 $62.96 on December 31, 2014, 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, 2014 was approximately $2.7 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 vest 50% upon the first anniversary of the grant date, with the remaining 50% vesting in equal installments of 12.5% each quarter thereafter so that all DSUs are 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, 2014:
		Units			Weighted Average Grant Date Fair Value
		(in thousands)
	Outstanding at January 1, 2014	238			$	32.01
	Granted	48			54.06
	Vested and distributed	(26	)		30.53
	Outstanding at December 31, 2014	260			$	36.35
	The total pre-tax intrinsic value of DSUs that were vested and distributed during the years ended December 31, 2014, 2013 and 2012 was $1.4 million, $3.8 million and $2.3 million, respectively. The total fair value of DSUs that were vested and distributed during the years ended December 31, 2014, 2013 and 2012 was $0.8 million, $1.5 million and $2.4 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, 2014, 57,000 DSUs were unvested, with an aggregate intrinsic value of approximately $3.6 million and a weighted average remaining contractual life of approximately 6.2 years. These units are expected to vest on various dates through May 2015.
	Restricted Stock Units
	The following table summarizes the different types of restricted stock units ("RSUs") granted by the Company during the years ended December 31, 2014, 2013 and 2012 (in thousands):
		31-Dec-14			31-Dec-13			31-Dec-12
	RSUs with service-based vesting conditions	1,949			2,338			2,782
	RSUs with performance-based vesting conditions	575			760			369
	Total	2,524			3,098			3,151
	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, as well as RSUs that vest only upon the achievement of defined performance metrics tied primarily to corporate revenue and earnings per share targets or other key performance indicators.
	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.
For the years ended December 31, 2014, 2013 and 2012, management measured compensation expense for performance-based RSUs based upon a review of the Company’s expected achievement against specified 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. Management will continue to periodically review the Company’s expected performance and adjust the compensation cost, if needed, at such time.
The following table summarizes the RSU activity for the year ended December 31, 2014:
	Units			Weighted Average Grant Date Fair Value
	(in thousands)
Outstanding at January 1, 2014	5,538			$	36.43
Granted	2,524			59.72
Vested	(2,504	)		34.7
Forfeited	(1,016	)		42.2
Outstanding at December 31, 2014	4,542			$	48.98
The total pre-tax intrinsic value of RSUs that vested during the years ended December 31, 2014, 2013 and 2012 was $145.6 million, $117.5 million and $98.3 million, respectively. The total fair value of RSUs that vested during the years ended December 31, 2014, 2013 and 2012 was $86.9 million, $89.2 million and $71.4 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, 2014, 4.5 million RSUs were outstanding and unvested, with an aggregate intrinsic value of $285.7 million and a weighted average remaining contractual life of approximately 5.6 years. These RSUs are expected to vest on various dates through November 2018.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The components of income before provision for income taxes were as follows for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	U.S.	$	408,391			$	365,821			$	245,252
	Foreign	71,385				53,733				76,339
	Income before provision for income taxes	$	479,776			$	419,554			$	321,591
	The provision for income taxes consisted of the following for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	Current tax provision:
	Federal	$	153,471			$	77,671			$	94,423
	State	4,978				8,034				10,046
	Foreign	13,259				13,019				18,952
	Deferred tax (benefit) provision:
	Federal	(13,073		)		24,210				(582		)
	State	(15,220		)		(1,106		)		(2,045		)
	Foreign	2,442				1,869				(3,189		)
	Change in valuation allowance	(29		)		2,370				(3		)
	Total	$	145,828			$	126,067			$	117,602
	The Company’s effective rate differed from the U.S. federal statutory rate as follows for the years ended December 31, 2014, 2013 and 2012:
		2014			2013			2012
	U.S. federal income tax rate	35	%		35	%		35	%
	State taxes	2.3			3.4			3.5
	Nondeductible stock-based compensation	1.4			0.8			1.3
	U.S. federal and state research and development credits	(3.2	)		(3.5	)		(0.6	)
	Change in state tax rates	(0.3	)		—			(0.4	)
	Foreign earnings	(1.9	)		(2.6	)		(3.5	)
	Disallowed officer compensation	0.1			0.1			0.6
	Domestic production activities deduction	(2.2	)		(4.3	)		—
	Change in the deferred tax asset valuation allowance	—			0.6			—
	State software development activities	(2.4	)		—			—
	Other	1.6			0.5			0.7
		30.4	%		30	%		36.6	%
	The components of the net deferred tax asset and the related valuation allowance as of December 31, 2014 and 2013 were as follows (in thousands):
		2014				2013
	Accrued bonus	$	19,572			$	14,266
	Deferred revenue	9,536				5,691
	Deferred rent	10,518				6,738
	Stock-based compensation	27,538				30,125
	Net operating losses	11,466				14,392
	Tax credit carryforwards	18,066				11,107
	Other	7,276				5,361
	Deferred tax assets	103,972				87,680
	Depreciation and amortization	(14,868		)		(15,607		)
	Acquired intangible assets	(40,126		)		(19,530		)
	Internal-use software development costs capitalized	(39,396		)		(31,970		)
	Deferred tax liabilities	(94,390		)		(67,107		)
	Valuation allowance	(1,222		)		(1,251		)
	Net deferred tax assets	$	8,360			$	19,322
	As of December 31, 2014 and 2013, the Company had U.S. federal NOL carryforwards of approximately $26.1 million and $30.7 million related to acquisitions completed during 2012, which expire at various dates through 2029. As of December 31, 2014 and 2013, the Company had state NOL carryforwards of approximately $45.0 million and $59.0 million, respectively, which expire at various dates through 2034. The Company also had foreign NOL carryforwards of approximately $0.3 million and $2.4 million as of December 31, 2014 and 2013, respectively. The majority of the foreign NOL carryforwards have no expiration dates. As of December 31, 2014 and 2013, the Company had U.S. federal and state research and development tax credit carryforwards of $30.5 million and $10.0 million, respectively, which will expire at various dates through 2029. As of December 31, 2014, the Company had no foreign tax credit carryforwards. As of December 31, 2013, the Company had foreign tax credit carryforwards of $4.4 million.
	As of December 31, 2014 and 2013, the Company recorded a valuation allowance on its deferred tax assets of $1.2 million and $1.3 million, respectively, a decrease of $0.1 million.
	As of December 31, 2014, undistributed earnings of non-U.S. subsidiaries totaled $224.0 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 $45.0 million.
	During 2013 and 2012, the Company corrected immaterial errors in its reported income tax expense attributable to prior fiscal periods, which reduced income tax expense by $3.6 million and $5.3 million, respectively, during those years.
	The following is a rollforward of the Company’s unrecognized tax benefits for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	Balance at beginning of year	$	24,651			$	20,902			$	12,496
	Gross increases — tax positions of prior periods	12,925				2,878				12,173
	Gross increases — current-period tax positions	2,106				2,834				2,251
	Gross decreases — tax positions of prior periods	(6,362		)		(1,213		)		(6,018		)
	Gross decreases — settlements	—				(750		)		—
	Balance at end of year	$	33,320			$	24,651			$	20,902
	As of December 31, 2014, 2013 and 2012, the Company had approximately $41.1 million, $30.6 million and $26.9 million, respectively, of total unrecognized tax benefits, including $7.7 million of accrued interest and penalties as of December 31, 2014 and $5.9 million of accrued interest and penalties as of both December 31, 2013 and 2012. The Company's unrecognized tax benefits are included in other liabilities in the consolidated balance sheets. Interest and penalties related to unrecognized tax benefits are recorded in the provision for income taxes and were $1.8 million for the year ended December 31, 2014 and insignificant for the year ended December 31, 2013. Interest and penalties included in the provision for income taxes for the year ended December 31, 2012 were $1.2 million. If recognized, all amounts of unrecognized tax benefits would have resulted in a reduction of income tax expense, impacting the effective income tax rate.
	As of December 31, 2014, the Company believes it is reasonably possible that $4.3 million of its unrecognized tax benefits, each of which is individually insignificant, including research and development credits and transfer pricing adjustments, may be recognized by the end of 2015 as a result of ongoing audits.
	The Company's U.S. federal income tax returns for the 2012 and 2011 tax years are currently under audit by the Internal Revenue Service. In addition, certain state and foreign income tax returns from 2008 through 2013 are currently under audit in those jurisdictions. The Company does not expect the results of these examinations to have a material effect on its financial condition, results of operations or cash flows.
	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 2010 are open for examination.

Net_Income_per_Share

Net Income per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Income per Share	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, 2014, 2013 and 2012 (in thousands, except per share data):
		2014			2013			2012
	Numerator:
	Net income	$	333,948		$	293,487		$	203,989
	Denominator:
	Shares used for basic net income per share	178,279			178,196			177,900
	Effect of dilutive securities:
	Stock options	1,221			1,622			2,182
	RSUs and DSUs	1,686			1,965			1,667
	Convertible senior notes	—			—			—
	Warrants related to issuance of convertible senior notes	—			—			—
	Shares used for diluted net income per share	181,186			181,783			181,749
	Basic net income per share	$	1.87		$	1.65		$	1.15
	Diluted net income per share	$	1.84		$	1.61		$	1.12
	For the years ended December 31, 2014, 2013 and 2012, 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 would be 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, 2014, 2013 and 2012 (in thousands):
		2014		2013			2012
	Stock options	402		1,649			2,551
	Service-based restricted stock units	786		188			1,154
	Performance-based restricted stock units	570		985			1,734
	Convertible senior notes	—		—			—
	Warrants related to issuance of convertible senior notes	—		—			—
	Total shares excluded from computation	1,758		2,822			5,439
	The calculation of assumed proceeds used to determine the diluted weighted average shares outstanding under the treasury stock method in the periods presented was adjusted by tax windfalls and shortfalls associated with all of the Company’s outstanding stock awards. Such windfalls and shortfalls are computed by comparing the tax deductible amount of outstanding stock awards to their grant-date fair values and multiplying the results by the applicable statutory tax rate. A positive result creates a windfall, which increases the assumed proceeds, and a negative result creates a shortfall, which reduces the assumed proceeds.

Segment_and_Geographic_Informa

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2014
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, 2014, the Company operated in one industry segment: providing cloud services for delivering, optimizing and securing online content and business applications. 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 solutions and does not have separate operating or reportable segments.
	The Company deploys its servers into networks worldwide. As of December 31, 2014, the Company had approximately $249.5 million and $175.8 million of net property and equipment, excluding internal-use software, located in the U.S. and foreign locations, respectively. As of December 31, 2013, the Company had approximately $210.9 million and $124.9 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 $531.9 million, $432.6 million and $369.0 million for the years ended December 31, 2014, 2013 and 2012, respectively. Other than the U.S., no single country accounted for 10% or more of the Company’s total revenue for any reported period.

Quarterly_Financial_Results_un

Quarterly Financial Results (unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Results (unaudited)	Quarterly Financial Results (unaudited)
	(in thousands, except per share data)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
	Year ended December 31, 2014:
	Revenue	$	453,502	$	476,035	$	498,042	$	536,295
	Cost of revenue (exclusive of amortization of acquired intangible assets)	139,612		149,318		158,812		163,201
	Net income	72,800		72,886		91,155		97,107
	Basic net income per share	0.41		0.41		0.51		0.55
	Diluted net income per share	0.4		0.4		0.5		0.54
	Year ended December 31, 2013:
	Revenue	$	368,046	$	378,106	$	395,790	$	435,980
	Cost of revenue (exclusive of amortization of acquired intangible assets)	120,392		124,705		132,039		133,951
	Net income	71,487		61,895		79,756		80,349
	Basic net income per share	0.4		0.35		0.45		0.45
	Diluted net income per share	0.39		0.34		0.44		0.44

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
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, 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 more than three months at the date of purchase and less than one year from the date of the balance sheets 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 sheets.
	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 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 operations. 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 of, and business outlook for 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 operations. 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, 2014, 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, 2014, 2013 and 2012, no customer accounted for more than 10% of total revenue. As of December 31, 2014, no customers had an accounts receivable balance greater than 10% of total accounts receivable. As of December 31, 2013, one customer had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2014, 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.
	Effective January 1, 2013, the Company increased the expected average useful lives of its network assets, primarily servers, from three to four years to reflect software and hardware related initiatives to manage its global network more efficiently. This change was recorded prospectively and decreased depreciation expense on network assets for the years ended December 31, 2014 and 2013 by approximately $21.1 million and $45.7 million, respectively, and increased net income for the years ended December 31, 2014 and 2013 by approximately $15.5 million and $33.6 million, respectively. The change also increased both basic and diluted net income per share for the year ended December 31, 2014 by $0.09; and for the year ended December 31, 2013, by $0.19 and $0.18, respectively.
	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, 2014, 2013 and 2012, 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, 2014, 2013 and 2012.
	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. The Company did not have any impairments during the years ended December 31, 2014, 2013 and 2012.
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 all solution unit pricing 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 a reseller channel. 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 network operation, build-out and support and services delivery; 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 two 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 discounted 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 during the application development stage, as well as interest expense related to the Company's senior convertible notes. Capitalization begins when the planning stage is complete and the Company commits resources to the software project. Capitalization ceases when the software has been tested and is ready for its intended use. The Company amortizes completed internal-use software to cost of revenue over its estimated useful life. Costs incurred during the planning, training and post-implementation stages of the software development life-cycle are expensed as incurred.
Advertising Expense	Advertising Expense
	The Company recognizes advertising expense as incurred. The Company recognized total advertising expense of $2.7 million for each of the years ended December 31, 2014 and 2013, and $2.8 million for the year ended December 31, 2012.
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation
	The Company recognizes compensation costs for all stock-based payment awards made to employees and directors 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 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 operation.
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 (expense) income, 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 (expense) income, net. As of December 31, 2014 and 2013, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2014, 2013 and 2012 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 to determine the amount of tax benefit to be recognized. 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step analysis of transactions to determine when and how revenue is recognized.  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. This guidance will be effective for the Company on January 1, 2017 and may be applied retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption.  The Company is evaluating the potential impact of adopting this new accounting guidance.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities	The following is a summary of available-for-sale marketable securities held as of December 31, 2014 and 2013 (in thousands):
					Gross Unrealized						Aggregate			Classification on Balance Sheet
		Amortized Cost									Fair Value			Short-Term		Long-Term
														Marketable		Marketable
	As of December 31, 2014				Gains			Losses						Securities		Securities
	Certificates of deposit	$	39		$	—		$	—		$	39		$	—	$	39
	Commercial paper	10,487			—			(2		)	10,485			10,485		—
	Corporate bonds	1,077,387			454			(2,132		)	1,075,709			424,777		650,932
	U.S. government agency obligations	303,808			20			(427		)	303,401			84,380		219,021
		$	1,391,721		$	474		$	(2,561	)	$	1,389,634		$	519,642	$	869,992
	As of December 31, 2013
	Certificates of deposit	$	222		$	—		$	—		$	222		$	173	$	49
	Corporate bonds	736,945			1,197			(281		)	737,861			278,318		459,543
	U.S. government agency obligations	174,982			51			(85		)	174,948			61,514		113,434
		$	912,149		$	1,248		$	(366	)	$	913,031		$	340,005	$	573,026
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, 2014 and 2013 (in thousands):
		Total Fair Value			Fair Value Measurements at Reporting Date Using
					Level 1			Level 2			Level 3
	As of December 31, 2014
	Cash Equivalents and Marketable Securities:
	Money market funds	$	501		$	501		$	—		$	—
	Certificates of deposit	39			39			—			—
	Commercial paper	10,485			—			10,485			—
	Corporate bonds	1,075,709			—			1,075,709			—
	U.S. government agency obligations	303,401			—			303,401			—
		$	1,390,135		$	540		$	1,389,595		$	—
	Other Liabilities:
	Contingent consideration obligation related to Velocius acquisition	$	(900	)	$	—		$	—		$	(900	)
	As of December 31, 2013
	Cash Equivalents and Marketable Securities:
	Money market funds	$	40,482		$	40,482		$	—		$	—
	Certificates of deposit	3,418			3,418			—			—
	Commercial paper	29,999			—			29,999			—
	Corporate bonds	737,861			—			737,861			—
	U.S. government agency obligations	174,948			—			174,948			—
		$	986,708		$	43,900		$	942,808		$	—
	Other Assets:
	Note receivable	$	22,879		$	—		$	—		$	22,879
	Other Liabilities:
	Contingent consideration obligation related to Velocius acquisition	$	(2,600	)	$	—		$	—		$	(2,600	)
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, 2014 and 2013 were as follows (in thousands):
		December 31, 2014			December 31, 2013
	Due in 1 year or less	$	519,642		$	340,005
	Due after 1 year through 5 years	869,992			573,026
		$	1,389,634		$	913,031
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 assets and liabilities measured at fair value using Level 3 inputs for the years ended December 31, 2014 and 2013 (in thousands):
		Other Assets:			Other Liabilities:
		Note Receivable			Contingent Consideration Obligation
	Balance, January 1, 2013	$	—		$	(1,200	)
	Fair value adjustment to contingent consideration for acquisition of Verivue included in general and administrative expense	—			1,200
	Contingent consideration obligation related to Velocius acquisition	—			(2,600		)
	Convertible note receivable from divestiture of a business	18,882			—
	Unrealized gain on convertible note receivable included in other comprehensive income	3,997			—
	Balance, December 31, 2013	$	22,879		$	(2,600	)
	Fair value adjustment to Velocius contingent consideration included in general and administrative expense	—			(300		)
	Achievement of first milestone related to Velocius contingent consideration	—			2,000
	Unrealized gain on convertible note receivable included in other comprehensive income	2,121			—
	Amendment of the convertible note receivable for preferred stock of the issuer and cash	(25,000		)	—
	Balance, December 31, 2014	$	—		$	(900	)

Accounts_Receivable_Tables

Accounts Receivable (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013 (in thousands):
		December 31, 2014			December 31, 2013
	Trade accounts receivable	$	222,531		$	175,391
	Unbilled accounts receivable	116,070			100,300
	Gross accounts receivable	338,601			275,691
	Allowance for doubtful accounts	(1,033		)	(708		)
	Reserve for cash-basis customers	(7,990		)	(2,995		)
	Total accounts receivable reserves	(9,023		)	(3,703		)
	Accounts receivable, net	$	329,578		$	271,988
Schedule of Activity in the Accounts Receivable Reserves	A summary of activity in the accounts receivable reserves for the years ended December 31, 2014, 2013 and 2012, is as follows (in thousands):
		2014			2013			2012
	Beginning balance	$	3,703		$	3,807		$	4,555
	Charges to income from operations	32,293			17,900			15,599
	Collections from cash basis customers and write-offs	(26,973		)	(18,004		)	(16,347		)
	Ending balance	$	9,023		$	3,703		$	3,807

Prepaid_Expenses_and_Other_Cur1

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013 (in thousands):
		31-Dec-14		31-Dec-13
	Prepaid income taxes	$	44,631	$	3,249
	Other prepaid expenses	37,669		29,498
	Other current assets	46,681		29,349
	Total	$	128,981	$	62,096

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following as of December 31, 2014 and 2013 (dollars in thousands):
		31-Dec-14			31-Dec-13			Estimated Useful Life in Years
	Computer and networking equipment	$	850,533		$	737,957		4-Mar
	Purchased software	46,537			40,237			3
	Furniture and fixtures	27,923			20,838			5
	Office equipment	14,035			10,353			3
	Leasehold improvements	92,544			64,471			12-Feb
	Internal-use software	448,777			340,421			7-Feb
	Property and equipment, gross	1,480,349			1,214,277
	Accumulated depreciation and amortization	(878,758		)	(763,990		)
	Property and equipment, net	$	601,591		$	450,287

Goodwill_and_Acquired_Intangib1

Goodwill and Acquired Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013 were as follows (in thousands):
		2014		2013
	Beginning balance	$	757,368	$	723,701
	Additions	293,926		35,606
	Disposals	—		(1,939		)
	Ending balance	$	1,051,294	$	757,368
Schedule of Acquired Intangible Assets	Acquired intangible assets that are subject to amortization consisted of the following as of December 31, 2014 and 2013 (in thousands):
		December 31, 2014							December 31, 2013
		Gross		Accumulated			Net		Gross		Accumulated			Net
		Carrying		Amortization			Carrying		Carrying		Amortization			Carrying
		Amount					Amount		Amount					Amount
	Completed technologies	$	88,331	$	(45,537	)	$	42,794	$	65,631	$	(35,476	)	$	30,155
	Customer relationships	173,600		(91,160		)	82,440		115,100		(75,563		)	39,537
	Non-compete agreements	8,890		(4,224		)	4,666		7,950		(2,623		)	5,327
	Trademarks and trade names	3,700		(1,188		)	2,512		3,400		(990		)	2,410
	Acquired license rights	490		(490		)	—		490		(490		)	—
	Total	$	275,011	$	(142,599	)	$	132,412	$	192,571	$	(115,142	)	$	77,429

Business_Acquisitions_and_Dive1

Business Acquisitions and Divestitures (Tables)	12 Months Ended
	Dec. 31, 2014
Business Acquisition [Line Items]
Schedule of Acquired Intangible Assets	Acquired intangible assets that are subject to amortization consisted of the following as of December 31, 2014 and 2013 (in thousands):
		December 31, 2014									December 31, 2013
		Gross				Accumulated			Net		Gross		Accumulated			Net
		Carrying				Amortization			Carrying		Carrying		Amortization			Carrying
		Amount							Amount		Amount					Amount
	Completed technologies	$	88,331			$	(45,537	)	$	42,794	$	65,631	$	(35,476	)	$	30,155
	Customer relationships	173,600				(91,160		)	82,440		115,100		(75,563		)	39,537
	Non-compete agreements	8,890				(4,224		)	4,666		7,950		(2,623		)	5,327
	Trademarks and trade names	3,700				(1,188		)	2,512		3,400		(990		)	2,410
	Acquired license rights	490				(490		)	—		490		(490		)	—
	Total	$	275,011			$	(142,599	)	$	132,412	$	192,571	$	(115,142	)	$	77,429
Prolexic
Business Acquisition [Line Items]
Schedule of Purchase Price Allocation	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	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
	Trademark	800				4.9
	Total	$	87,040
Cotendo
Business Acquisition [Line Items]
Schedule of Purchase Price Allocation	The following table presents the final allocation of the purchase price of Cotendo (in thousands):
	Total purchase consideration	$	278,877
	Allocation of the purchase consideration:
	Current assets, including cash and cash equivalents of $6,405	$	6,751
	Trade receivables	2,920
	Property and equipment	5,812
	Indemnification assets	6,200
	Long-term assets	75
	Identifiable intangible assets	43,800
	Goodwill	233,828
	Deferred tax liabilities	(15,376		)
	Other liabilities assumed	(5,133		)
	Net assets acquired	$	278,877
Schedule of Acquired Intangible Assets	The following were the identified intangible assets acquired and their respective weighted average useful lives (in thousands, except for years):
		Gross				Weighted Average Useful Life (in years)
		Carrying
		Amount
	Completed technology	$	24,100			5.8
	Customer relationships	13,400				8.8
	Non-compete agreements	3,900				6
	Trademarks and trade names	2,400				9.8
	Total	$	43,800

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Accounts Payable and Accrued Liabilities, Current [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following as of December 31, 2014 and 2013 (in thousands):
		31-Dec-14		31-Dec-13
	Payroll and other related benefits	$	125,938	$	90,093
	Bandwidth and co-location	28,459		20,991
	Property, use and other taxes	40,411		32,503
	Professional service fees	4,434		4,388
	Other	5,444		2,410
	Total	$	204,686	$	150,385

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 were as follows (in thousands):
	2015	$	40,728
	2016	40,916
	2017	40,510
	2018	32,972
	2019	29,723
	Thereafter	38,412
	Total	$	223,261
Schedule of Long-Term Commitments	The minimum future commitments as of December 31, 2014 were as follows (in thousands):
		Bandwidth and Co-location Commitments		Purchase Order Commitments
	2015	$	119,081	$	115,014
	2016	20,028		5,708
	2017	10,313		2,470
	2018	365		795
	2019	92		—
	Thereafter	—		—
	Total	$	149,879	$	123,987

Convertible_Senior_Notes_Table

Convertible Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Convertible Senior Notes	The Notes consist of the following components as of December 31, 2014 (in thousands):
		December 31, 2014
	Liability component:
	Principal	$	690,000
	Less: debt discount, net of amortization	(85,149		)
	Net carrying amount	$	604,851
	Equity component:	$	101,276
Schedule of Interest Expense	The following table sets forth total interest expense included in the statement of operations related to the Notes for the year ended December 31, 2014 (in thousands):
		For the Year Ended December 31, 2014
	Amortization of debt discount	$	16,127
	Amortization of debt issuance costs	1,531
	Capitalization of interest expense	(2,195		)
	Total interest expense	$	15,463

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 (in thousands):
		Foreign Currency Translation			Net Unrealized Gains (Losses) on Investments			Total
	Balance, beginning of year	$	(6,715	)	$	4,624		$	(2,091	)
	Other comprehensive loss	(15,349		)	(171		)	(15,520		)
	Balance, end of year	$	(22,064	)	$	4,453		$	(17,611	)

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Stock Based Compensation Expense	The following table summarizes the components of total stock-based compensation expense included in the Company’s consolidated statements of operations for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	Cost of revenue	$	11,934			$	10,867			$	11,309
	Research and development expense	19,341				17,472				17,275
	Sales and marketing expense	47,570				39,290				34,322
	General and administrative expense	33,151				28,255				27,679
	Total stock-based compensation	111,996				95,884				90,585
	Provision for income taxes	(39,182		)		(34,829		)		(33,126		)
	Total stock-based compensation, net of taxes	$	72,814			$	61,055			$	57,459
Schedule of Stock Options Granted Black Scholes	The grant-date fair values of the Company's stock option awards granted during the years ended December 31, 2014, 2013 and 2012 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		2014			2013			2012
	Expected term (in years)	4.4			4.5			4.2
	Risk-free interest rate	0.8	%		0.8	%		0.6	%
	Expected volatility	40.4	%		44.4	%		50.8	%
	Dividend yield	—	%		—	%		—	%
Schedule of ESPP Granted Black Scholes	The grant-date fair values of the Company's ESPP awards granted during the years ended December 31, 2014, 2013 and 2012 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:
		2014			2013			2012
	Expected term (in years)	0.5			0.5			0.5
	Risk-free interest rate	0.1	%		0.1	%		0.1	%
	Expected volatility	33.5	%		42	%		51	%
	Dividend yield	—	%		—	%		—	%
Schedule of Summary of Stock Option Activity	The following table summarizes stock option activity during the year ended December 31, 2014:
		Shares			Weighted Average Exercise Price				Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
		(in thousands)							(in years)		(in thousands)
	Outstanding at January 1, 2014	4,458			$	30.67
	Granted	352			12.73
	Exercised	(1,978	)		28.87
	Forfeited	(161	)		47.02
	Outstanding at December 31, 2014	2,671			$	28.65			3.48		$	168,706
	Exercisable at December 31, 2014	1,933			$	28.66			2.68		$	121,722
	Vested or expected to vest December 31, 2014	2,662			$	28.52			3.45		$	167,600
Schedule Of Deferred Stock Units Activity	The following table summarizes the DSU activity for the year ended December 31, 2014:
		Units			Weighted Average Grant Date Fair Value
		(in thousands)
	Outstanding at January 1, 2014	238			$	32.01
	Granted	48			54.06
	Vested and distributed	(26	)		30.53
	Outstanding at December 31, 2014	260			$	36.35
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 years ended December 31, 2014, 2013 and 2012 (in thousands):
		31-Dec-14			31-Dec-13			31-Dec-12
	RSUs with service-based vesting conditions	1,949			2,338			2,782
	RSUs with performance-based vesting conditions	575			760			369
	Total	2,524			3,098			3,151
Schedule of Restricted Stock Units Activity	The following table summarizes the RSU activity for the year ended December 31, 2014:
		Units			Weighted Average Grant Date Fair Value
		(in thousands)
	Outstanding at January 1, 2014	5,538			$	36.43
	Granted	2,524			59.72
	Vested	(2,504	)		34.7
	Forfeited	(1,016	)		42.2
	Outstanding at December 31, 2014	4,542			$	48.98

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	U.S.	$	408,391			$	365,821			$	245,252
	Foreign	71,385				53,733				76,339
	Income before provision for income taxes	$	479,776			$	419,554			$	321,591
Schedule of Provision for Income Tax	The provision for income taxes consisted of the following for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	Current tax provision:
	Federal	$	153,471			$	77,671			$	94,423
	State	4,978				8,034				10,046
	Foreign	13,259				13,019				18,952
	Deferred tax (benefit) provision:
	Federal	(13,073		)		24,210				(582		)
	State	(15,220		)		(1,106		)		(2,045		)
	Foreign	2,442				1,869				(3,189		)
	Change in valuation allowance	(29		)		2,370				(3		)
	Total	$	145,828			$	126,067			$	117,602
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, 2014, 2013 and 2012:
		2014			2013			2012
	U.S. federal income tax rate	35	%		35	%		35	%
	State taxes	2.3			3.4			3.5
	Nondeductible stock-based compensation	1.4			0.8			1.3
	U.S. federal and state research and development credits	(3.2	)		(3.5	)		(0.6	)
	Change in state tax rates	(0.3	)		—			(0.4	)
	Foreign earnings	(1.9	)		(2.6	)		(3.5	)
	Disallowed officer compensation	0.1			0.1			0.6
	Domestic production activities deduction	(2.2	)		(4.3	)		—
	Change in the deferred tax asset valuation allowance	—			0.6			—
	State software development activities	(2.4	)		—			—
	Other	1.6			0.5			0.7
		30.4	%		30	%		36.6	%
Net Deferred Tax and Valuation Allowance	The components of the net deferred tax asset and the related valuation allowance as of December 31, 2014 and 2013 were as follows (in thousands):
		2014				2013
	Accrued bonus	$	19,572			$	14,266
	Deferred revenue	9,536				5,691
	Deferred rent	10,518				6,738
	Stock-based compensation	27,538				30,125
	Net operating losses	11,466				14,392
	Tax credit carryforwards	18,066				11,107
	Other	7,276				5,361
	Deferred tax assets	103,972				87,680
	Depreciation and amortization	(14,868		)		(15,607		)
	Acquired intangible assets	(40,126		)		(19,530		)
	Internal-use software development costs capitalized	(39,396		)		(31,970		)
	Deferred tax liabilities	(94,390		)		(67,107		)
	Valuation allowance	(1,222		)		(1,251		)
	Net deferred tax assets	$	8,360			$	19,322
Unrecognized Tax Benefits	The following is a rollforward of the Company’s unrecognized tax benefits for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		2014				2013				2012
	Balance at beginning of year	$	24,651			$	20,902			$	12,496
	Gross increases — tax positions of prior periods	12,925				2,878				12,173
	Gross increases — current-period tax positions	2,106				2,834				2,251
	Gross decreases — tax positions of prior periods	(6,362		)		(1,213		)		(6,018		)
	Gross decreases — settlements	—				(750		)		—
	Balance at end of year	$	33,320			$	24,651			$	20,902

Net_Income_per_Share_Tables

Net Income per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Components Used in Diluted and Basic Income Per Common Share	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, 2014, 2013 and 2012 (in thousands, except per share data):
		2014			2013			2012
	Numerator:
	Net income	$	333,948		$	293,487		$	203,989
	Denominator:
	Shares used for basic net income per share	178,279			178,196			177,900
	Effect of dilutive securities:
	Stock options	1,221			1,622			2,182
	RSUs and DSUs	1,686			1,965			1,667
	Convertible senior notes	—			—			—
	Warrants related to issuance of convertible senior notes	—			—			—
	Shares used for diluted net income per share	181,186			181,783			181,749
	Basic net income per share	$	1.87		$	1.65		$	1.15
	Diluted net income per share	$	1.84		$	1.61		$	1.12
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, 2014, 2013 and 2012 (in thousands):
		2014		2013			2012
	Stock options	402		1,649			2,551
	Service-based restricted stock units	786		188			1,154
	Performance-based restricted stock units	570		985			1,734
	Convertible senior notes	—		—			—
	Warrants related to issuance of convertible senior notes	—		—			—
	Total shares excluded from computation	1,758		2,822			5,439

Quarterly_Financial_Results_un1

Quarterly Financial Results (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014:
	Revenue	$	453,502	$	476,035	$	498,042	$	536,295
	Cost of revenue (exclusive of amortization of acquired intangible assets)	139,612		149,318		158,812		163,201
	Net income	72,800		72,886		91,155		97,107
	Basic net income per share	0.41		0.41		0.51		0.55
	Diluted net income per share	0.4		0.4		0.5		0.54
	Year ended December 31, 2013:
	Revenue	$	368,046	$	378,106	$	395,790	$	435,980
	Cost of revenue (exclusive of amortization of acquired intangible assets)	120,392		124,705		132,039		133,951
	Net income	71,487		61,895		79,756		80,349
	Basic net income per share	0.4		0.35		0.45		0.45
	Diluted net income per share	0.39		0.34		0.44		0.44

Nature_of_Business_and_Basis_o1

Nature of Business and Basis of Presentation - Narrative (Details)	12 Months Ended
	Dec. 31, 2014
	segment
	server
	country
	network
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of servers (in servers) (more than 170,000 servers)	170,000
Number of networks (in networks)	1,300
Number of countries with servers and networks (in countries) (over 100 countries)	100
Number of operating segments (in number of segments)	1

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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
Advertising expense	2,700,000	2,700,000	2,800,000
Minimum percentage of tax benefit to be recognized (in percentage)	50.00%
Historical useful life | Computer and networking equipment
Summary of Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives (in years)	3 years
Service life | Computer and networking equipment
Summary of Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful lives (in years)	4 years
Reduced depreciation
Summary of Significant Accounting Policies [Line Items]
Change in accounting estimate, financial impact	21,100,000	45,700,000
Increased net income
Summary of Significant Accounting Policies [Line Items]
Change in accounting estimate, financial impact	$15,500,000	$33,600,000
Increased basic net Income per share
Summary of Significant Accounting Policies [Line Items]
Change in accounting estimate, financial impact (in dollars per share)		$0.19
Increased diluted net Income per share
Summary of Significant Accounting Policies [Line Items]
Change in accounting estimate, financial impact (in dollars per share)	$0.09	$0.18
Sales | Customer concentration risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, number of customers (in whole numbers)	0	0	0
Concentration risk, percentage (in percentage)	10.00%	10.00%	10.00%
Accounts receivable | Customer concentration risk
Summary of Significant Accounting Policies [Line Items]
Concentration risk, number of customers (in whole numbers)	0	1
Concentration risk, percentage (in percentage)	10.00%	10.00%

Fair_Value_Measurements_Narrat

Fair Value Measurements - Narrative (Details) (ADS Divesiture [Member], USD $)	3 Months Ended	9 Months Ended
	Jun. 30, 2014	Sep. 30, 2014	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Convertible note receivable converted to preferred stock amount	$12,500,000
Proceeds from conversion of note receivable		12,500,000
Level 3
Schedule of Available-for-sale Securities [Line Items]
Face value of convertible note receivable received for divestiture of a business			$25,000,000

Fair_Value_Measurements_Market

Fair Value Measurements - Marketable Securities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	$1,391,721	$912,149
Gross unrealized gains	474	1,248
Gross unrealized losses	-2,561	-366
Available-for-sale securities	1,389,634	913,031
Short-term marketable securities	519,642	340,005
Long-term marketable securities	869,992	573,026
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	39	222
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Available-for-sale securities	39	222
Short-term marketable securities	0	173
Long-term marketable securities	39	49
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	10,487
Gross unrealized gains	0
Gross unrealized losses	-2
Available-for-sale securities	10,485
Short-term marketable securities	10,485
Long-term marketable securities	0
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	1,077,387	736,945
Gross unrealized gains	454	1,197
Gross unrealized losses	-2,132	-281
Available-for-sale securities	1,075,709	737,861
Short-term marketable securities	424,777	278,318
Long-term marketable securities	650,932	459,543
U.S. government agency obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, cost	303,808	174,982
Gross unrealized gains	20	51
Gross unrealized losses	-427	-85
Available-for-sale securities	303,401	174,948
Short-term marketable securities	84,380	61,514
Long-term marketable securities	$219,021	$113,434

Fair_Value_Measurements_Schedu

Fair Value Measurements - Schedule of Fair Value Measurement (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Cash Equivalents and Marketable Securities:
Available-for-sale securities	$1,389,634	$913,031
Level 1
Cash Equivalents and Marketable Securities:
Assets, fair value	540	43,900
Other Assets:
Note receivable		0
Other Liabilities:
Contingent consideration obligation related to Velocius acquisition	0	0
Level 2
Cash Equivalents and Marketable Securities:
Assets, fair value	1,389,595	942,808
Other Assets:
Note receivable		0
Other Liabilities:
Contingent consideration obligation related to Velocius acquisition	0	0
Level 3
Cash Equivalents and Marketable Securities:
Assets, fair value	0	0
Other Assets:
Note receivable		22,879
Other Liabilities:
Contingent consideration obligation related to Velocius acquisition	-900	-2,600
Money market funds | Level 1
Cash Equivalents and Marketable Securities:
Cash equivalents	501	40,482
Money market funds | Level 2
Cash Equivalents and Marketable Securities:
Cash equivalents	0	0
Money market funds | Level 3
Cash Equivalents and Marketable Securities:
Cash equivalents	0	0
Certificates of deposit
Cash Equivalents and Marketable Securities:
Available-for-sale securities	39	222
Certificates of deposit | Level 1
Cash Equivalents and Marketable Securities:
Available-for-sale securities	39	3,418
Certificates of deposit | Level 2
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Certificates of deposit | Level 3
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	10,485
Commercial paper | Level 1
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Commercial paper | Level 2
Cash Equivalents and Marketable Securities:
Available-for-sale securities	10,485	29,999
Commercial paper | Level 3
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	303,401	174,948
U.S. government agency obligations | Level 1
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
U.S. government agency obligations | Level 2
Cash Equivalents and Marketable Securities:
Available-for-sale securities	303,401	174,948
U.S. government agency obligations | Level 3
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	1,075,709	737,861
Corporate bonds | Level 1
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Corporate bonds | Level 2
Cash Equivalents and Marketable Securities:
Available-for-sale securities	1,075,709	737,861
Corporate bonds | Level 3
Cash Equivalents and Marketable Securities:
Available-for-sale securities	0	0
Total Fair Value
Cash Equivalents and Marketable Securities:
Assets, fair value	1,390,135	986,708
Other Assets:
Note receivable		22,879
Other Liabilities:
Contingent consideration obligation related to Velocius acquisition	-900	-2,600
Total Fair Value | Money market funds
Cash Equivalents and Marketable Securities:
Cash equivalents	501	40,482
Total Fair Value | Certificates of deposit
Cash Equivalents and Marketable Securities:
Available-for-sale securities	39	3,418
Total Fair Value | Commercial paper
Cash Equivalents and Marketable Securities:
Available-for-sale securities	10,485	29,999
Total Fair Value | U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Available-for-sale securities	303,401	174,948
Total Fair Value | Corporate bonds
Cash Equivalents and Marketable Securities:
Available-for-sale securities	$1,075,709	$737,861

Fair_Value_Measurements_Schedu1

Fair Value Measurements - Schedule of Contractual Maturities of Marketable Securities and Other Investment Related Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value Disclosures [Abstract]
Due in 1 year or less	$519,642	$340,005
Due after 1 year through 5 years	869,992	573,026
Available-for-sale securities	$1,389,634	$913,031

Fair_Value_Measurements_Schedu2

Fair Value Measurements - Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs (Details) (Level 3, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, Other Assets:Note Receivable	$22,879	$0
Beginning balance, Other Liabilities:Contingent Consideration Obligation	-2,600	-1,200
Convertible note receivable from divestiture of a business		18,882
Unrealized gain on convertible note receivable included in other comprehensive income	2,121	3,997
Amendment of the convertible note receivable for preferred stock of the issuer and cash	-25,000
Ending balance, Other Assets:Note Receivable	0	22,879
Ending balance, Other Liabilities:Contingent Consideration Obligation	-900	-2,600
Verivue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value adjustment to contingent consideration for acquisition included in general and administrative expense		1,200
Velocius
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value adjustment to contingent consideration for acquisition included in general and administrative expense	-300
Contingent consideration obligation related to Velocius acquisition		-2,600
Achievement of first milestone related to Velocius contingent consideration	$2,000

Accounts_Receivable_Schedule_o

Accounts Receivable - Schedule of Accounts Receivable (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$338,601	$275,691
Allowance for doubtful accounts	-1,033	-708
Reserve for cash-basis customers	-7,990	-2,995
Total accounts receivable reserves	-9,023	-3,703
Accounts receivable, net	329,578	271,988
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	222,531	175,391
Unbilled Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$116,070	$100,300

Accounts_Receivable_Activity_i

Accounts Receivable - Activity in Accounts Receivable Reserves (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$3,703	$3,807	$4,555
Charges to income from operations	32,293	17,900	15,599
Collections from cash basis customers	-26,973	-18,004	-16,347
Ending balance	$9,023	$3,703	$3,807

Prepaid_Expenses_and_Other_Cur2

Prepaid Expenses and Other Current Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid income taxes	$44,631	$3,249
Other prepaid expenses	37,669	29,498
Other current assets	46,681	29,349
Total	$128,981	$62,096

Property_and_Equipment_Narrati

Property and Equipment - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, software and equipment depreciation, amortization expense	$215,300,000	$162,900,000	$183,200,000
Capitalization of stock-based compensation	15,226,000	12,325,000	9,276,000
Impairment of long-lived assets held-for-use	100,100,000	68,500,000
Internal-use software
Property, Plant and Equipment [Line Items]
Capitalization of stock-based compensation	$15,200,000	$12,300,000	$9,300,000

Property_and_Equipment_Schedul

Property and Equipment - Schedule of Property and Equipment (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$1,480,349	$1,214,277
Accumulated depreciation and amortization	-878,758	-763,990
Property and equipment, net	601,591	450,287
Computer and networking equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	850,533	737,957
Purchased software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	46,537	40,237
Estimated useful life (in years)	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,923	20,838
Estimated useful life (in years)	5 years
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,035	10,353
Estimated useful life (in years)	3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	92,544	64,471
Internal-use software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$448,777	$340,421
Minimum | Computer and networking 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)	2 years
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)	4 years
Maximum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	12 years
Maximum | Internal-use software
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	7 years

Goodwill_and_Acquired_Intangib2

Goodwill and Acquired Intangible Assets - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$32,057,000	$21,547,000	$20,962,000
Future amortization expense, 2015	26,800,000
Future amortization expense, 2016	25,200,000
Future amortization expense, 2017	23,100,000
Future amortization expense, 2018	16,200,000
Future amortization expense, 2019	$12,600,000

Goodwill_and_Acquired_Intangib3

Goodwill and Acquired Intangible Assets - Schedule of the Changes in the Carrying Amount of Goodwill (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Changes in the carrying amount of goodwill
Beginning balance	$757,368	$723,701
Additions	293,926	35,606
Disposals	0	-1,939
Ending balance	$1,051,294	$757,368

Goodwill_and_Acquired_Intangib4

Goodwill and Acquired Intangible Assets - Schedule of Other Intangible Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$275,011	$192,571
Accumulated amortization	-142,599	-115,142
Net carrying amount	132,412	77,429
Completed technologies
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	88,331	65,631
Accumulated amortization	-45,537	-35,476
Net carrying amount	42,794	30,155
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	173,600	115,100
Accumulated amortization	-91,160	-75,563
Net carrying amount	82,440	39,537
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	8,890	7,950
Accumulated amortization	-4,224	-2,623
Net carrying amount	4,666	5,327
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	3,700	3,400
Accumulated amortization	-1,188	-990
Net carrying amount	2,512	2,410
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_Dive2

Business Acquisitions and Divestitures (Details) (USD $)

12 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

0 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Jun. 30, 2014

Sep. 30, 2014

Feb. 18, 2014

Nov. 08, 2013

Nov. 30, 2012

Dec. 31, 2014

Sep. 30, 2013

Dec. 04, 2012

Sep. 13, 2012

Mar. 06, 2012

Feb. 07, 2012

Business Acquisition [Line Items]

Acquisition related costs

$4,200,000

$3,100,000

$5,800,000

Allocation of the purchase consideration:

Goodwill

1,051,294,000

757,368,000

723,701,000

1,051,294,000

ADS Divesiture [Member]

Intangible assets acquired

Convertible note receivable converted to preferred stock amount

12,500,000

Proceeds from conversion of note receivable

12,500,000

ADS Divesiture [Member] | Level 3

Business Acquisition [Line Items]

Face value of convertible note receivable received for divestiture of a business

25,000,000

25,000,000

Prolexic

Business Acquisition [Line Items]

Total purchase consideration

392,104,000

Measurement period adjustment, increase (decrease) in goodwill

2,200,000

Goodwill, expected tax deductible amount

62,400,000

Allocation of the purchase consideration:

Cash

33,072,000

Accounts receivable

11,208,000

Property and equipment

12,225,000

Identifiable intangible assets

87,040,000

Goodwill

293,926,000

Deferred tax assets

16,340,000

Other current and long-term assets

5,664,000

Total assets acquired

459,475,000

Other current liabilities

-5,940,000

Current deferred revenue

-5,812,000

Deferred tax liabilities

-36,203,000

Other liabilities assumed

-19,416,000

Total liabilities assumed

-67,371,000

Net assets acquired

392,104,000

Intangible assets acquired

Gross carrying amount

87,040,000

Weighted average useful life (in years)

9 years 2 months 12 days

Prolexic | Completed technologies

Intangible assets acquired

Gross carrying amount

26,800,000

Weighted average useful life (in years)

6 years 11 months

Prolexic | Customer relationships

Intangible assets acquired

Gross carrying amount

58,500,000

Weighted average useful life (in years)

10 years 5 months

Prolexic | Non-compete agreements

Intangible assets acquired

Gross carrying amount

940,000

Weighted average useful life (in years)

3 years

Prolexic | Trademarks and trade names

Intangible assets acquired

Gross carrying amount

800,000

Weighted average useful life (in years)

4 years 11 months

Velocius

Business Acquisition [Line Items]

Total purchase consideration

4,300,000

Contingent consideration liability

900,000

2,600,000

900,000

Maximum potential payout of the contingent consideration

3,000,000

Goodwill, expected tax deductible amount

300,000

Allocation of the purchase consideration:

Identifiable intangible assets

2,500,000

Goodwill

5,400,000

Intangible assets acquired

Weighted average useful life (in years)

7 years 10 months 24 days

Strategic Network

Business Acquisition [Line Items]

Total purchase consideration

55,000,000

Cost of acquired entity, cash paid

27,500,000

27,500,000

Goodwill, expected tax deductible amount

30,200,000

Allocation of the purchase consideration:

Identifiable intangible assets

16,100,000

Goodwill

30,200,000

Intangible assets acquired

Weighted average useful life (in years)

9 years 9 months 18 days

Verivue

Business Acquisition [Line Items]

Total purchase consideration

30,900,000

Measurement period adjustment, increase (decrease) in goodwill

-5,800,000

Contingent consideration liability

1,200,000

Goodwill, expected tax deductible amount

3,000,000

Allocation of the purchase consideration:

Identifiable intangible assets

7,500,000

Goodwill

14,900,000

Intangible assets acquired

Weighted average useful life (in years)

6 years 4 months 24 days

FastSoft

Business Acquisition [Line Items]

Total purchase consideration

14,400,000

Measurement period adjustment, increase (decrease) in goodwill

-1,800,000

Goodwill, expected tax deductible amount

1,700,000

Allocation of the purchase consideration:

Identifiable intangible assets

3,700,000

Goodwill

7,100,000

Intangible assets acquired

Weighted average useful life (in years)

9 years

Cotendo

Business Acquisition [Line Items]

Total purchase consideration

278,877,000

Measurement period adjustment, increase (decrease) in goodwill

-7,800,000

Goodwill, expected tax deductible amount

44,400,000

Allocation of the purchase consideration:

Current assets, including cash and cash equivalents of $6,405

6,751,000

Cash

6,405,000

Accounts receivable

2,920,000

Property and equipment

5,812,000

Indemnification assets

6,200,000

Long-term assets

75,000

Identifiable intangible assets

43,800,000

Goodwill

233,828,000

Deferred tax liabilities

-15,376,000

Other liabilities assumed

-5,133,000

Net assets acquired

278,877,000

Intangible assets acquired

Gross carrying amount

43,800,000

Weighted average useful life (in years)

7 years 1 month 6 days

Cotendo | Completed technologies

Intangible assets acquired

Gross carrying amount

24,100,000

Weighted average useful life (in years)

5 years 9 months 18 days

Cotendo | Customer relationships

Intangible assets acquired

Gross carrying amount

13,400,000

Weighted average useful life (in years)

8 years 9 months 18 days

Cotendo | Non-compete agreements

Intangible assets acquired

Gross carrying amount

3,900,000

Weighted average useful life (in years)

6 years

Cotendo | Trademarks and trade names

Intangible assets acquired

Gross carrying amount

2,400,000

Weighted average useful life (in years)

9 years 9 months 18 days

Blaze

Business Acquisition [Line Items]

Total purchase consideration

19,300,000

Goodwill, expected tax deductible amount

13,500,000

Allocation of the purchase consideration:

Identifiable intangible assets

5,100,000

Goodwill

$15,100,000

Intangible assets acquired

Weighted average useful life (in years)

5 years 3 months 18 days

Accrued_Expenses_Schedule_of_A

Accrued Expenses - Schedule of Accrued Expenses and Other Current Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts Payable and Accrued Liabilities, Current [Abstract]
Payroll and other related benefits	$125,938	$90,093
Bandwidth and co-location	28,459	20,991
Property, use and other taxes	40,411	32,503
Professional service fees	4,434	4,388
Other	5,444	2,410
Total	$204,686	$150,385

Commitments_and_Contingencies_1

Commitments and Contingencies - Minimum Aggregate Future Obligations Under Non-cancelable Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
2015	$40,728,000
2016	40,916,000
2017	40,510,000
2018	32,972,000
2019	29,723,000
Thereafter	38,412,000
Total	223,261,000
Rent expense	39,900,000	30,800,000	23,500,000
Proceeds from sublease tenants	3,400,000	1,900,000	1,400,000
Letters of credit for real estate leases	$8,300,000
Percentage revenue representation for investigation of sales practices (less than 1%)	1.00%	1.00%	1.00%

Commitments_and_Contingencies_2

Commitments and Contingencies - Purchase Commitments (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Bandwidth and Co-location Commitments
Unrecorded Unconditional Purchase Obligation [Line Items]
2015	$119,081
2016	20,028
2017	10,313
2018	365
2019	92
Thereafter	0
Total	149,879
Purchase Order Commitments
Unrecorded Unconditional Purchase Obligation [Line Items]
2015	115,014
2016	5,708
2017	2,470
2018	795
2019	0
Thereafter	0
Total	$123,987

Convertible_Senior_Notes_Narra

Convertible Senior Notes - Narrative (Details) (USD $)	1 Months Ended	12 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Feb. 28, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	D
Debt Instrument [Line Items]
Debt issued	$690,000,000	$690,000,000
Conversion rate (in shares)	11.1651
Principal amount per conversion	1,000
Conversion price (in dollars per share)	$89.56
Threshold trading days exceeding price	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
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)	7.7
Fair value of convertible senior notes		720,900,000
Closing stock price (in dollars per share)		$62.96
Repurchases of common stock	62,000,000	268,647,000	160,419,000	141,468,000
Payments for purchase of convertible note hedge and warrant transactions	23,300,000
Payments for note hedge transactions	101,300,000	101,292,000	0	0
Note hedge shares outstanding (in shares)	7.7
Warrants outstanding (in shares)	7.7
Warrant strike price (in dollars per share)	$104.49
Proceeds from sale of warrants	$78,000,000	$77,970,000	$0	$0
Effective interest rate	3.20%

Convertible_Senior_Notes_Sched

Convertible Senior Notes - Schedule of Convertible Senior Notes (Details) (USD $)	Dec. 31, 2014	Feb. 28, 2014	Dec. 31, 2013
Liability component:
Principal	$690,000,000	$690,000,000
Less: debt discount, net of amortization	-85,149,000
Net carrying amount	604,851,000		0
Convertible senior notes
Liability component:
Equity component:	$101,276,000

Convertible_Senior_Notes_Sched1

Convertible Senior Notes - Schedule of Interest Expense (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Amortization of debt discount	$16,127
Amortization of debt issuance costs	1,531
Capitalization of interest expense	-2,195
Total interest expense	$15,463	$0	$0

Stockholders_Equity_Narrative_

Stockholders' Equity - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2013
Class of Stock [Line Items]
Amount of common stock repurchases authorized				$750,000,000
Value of shares repurchased during period	268,647,000	160,418,000	141,468,000
Remaining amount available for future purchases of shares under approved repurchase program.	433,600,000
Common Stock
Class of Stock [Line Items]
Repurchases of common stock (in shares)	4,629,000	3,900,000	4,400,000
Value of shares repurchased during period	$268,600,000	$160,400,000	$141,500,000

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Changes in accumulated other comprehensive loss
Balance, beginning of year	($2,091)
Other comprehensive loss	-15,520	-451	-381
Balance, end of year	-17,611	-2,091
Foreign Currency Translation
Changes in accumulated other comprehensive loss
Balance, beginning of year	-6,715
Other comprehensive loss	-15,349
Balance, end of year	-22,064
Net Unrealized Gains (Losses) on Investments
Changes in accumulated other comprehensive loss
Balance, beginning of year	4,624
Other comprehensive loss	-171
Balance, end of year	$4,453

Employee_Benefit_Plan_Narrativ

Employee Benefit Plan - Narrative (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation Related Costs [Abstract]
Contributions by employer	$16.60	$11.10	$6.40

StockBased_Compensation_Narrat

Stock-Based Compensation - Narrative (Details) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax unrecognized compensation cost	$145.10
Weighted average period for recognizing compensation cost (in years)	1 year 2 months
Closing stock price (in dollars per share)	$62.96
In the money options exercisable (in shares)	2,700,000
Prolexic
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options acquired in acquisition	328,000
Capitalized Internal Use Software
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional stock based compensation	10.3	8.1	7.7
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of stock options granted (in dollars per share)	$49.67	$14.17	$25.20
Total pre-tax intrinsic value of options exercised	45.8	47.2	47.9
Total fair value of vested options	16.9	12.4	16.6
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)	$12.64	$11.34	$8.71
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)	$54.06
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	3.8	2.3
Total fair value of vested and distributed	0.8	1.5	2.4
Unvested deferred stock units (in shares)	57,000
Aggregate intrinsic value	3.6
Weighted average contractual remaining life (in years)	6 years 2 months
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)	$59.72
Total pre-tax intrinsic value end of year	145.6	117.5	98.3
Total fair value of vested and distributed	86.9	89.2	71.4
Aggregate intrinsic value	285.7
Weighted average contractual remaining life (in years)	5 years 7 months
Each RSU receives this number of shares of common stock upon vesting (in shares)	1
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)	4,500,000
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)	8,000,000
Common stock available for grant (in shares)	10,200,000
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
Aggregate amount of shares available, maximum (in shares)	20,000,000
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)	700,000	600,000	700,000
Weighted average purchase price (in dollars per share)	$41.76	$34.26	$24.76
Total cash proceeds from shares purchased	29.3	22.1	16.8
Amount withheld from employees for future purchases	$3

StockBased_Compensation_Schedu

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$111,996	$95,884	$90,585
Provision for income taxes	-39,182	-34,829	-33,126
Total stock-based compensation, net of taxes	72,814	61,055	57,459
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	11,934	10,867	11,309
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	19,341	17,472	17,275
Sales and marketing expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	47,570	39,290	34,322
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$33,151	$28,255	$27,679

StockBased_Compensation_Schedu1

Stock-Based Compensation - Schedule of Stock Options Granted Black Scholes (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Expected term (in years)	4 years 5 months	4 years 6 months 4 days	4 years 2 months 12 days
Risk-free interest rate	0.80%	0.80%	0.60%
Expected volatility	40.40%	44.40%	50.80%
Dividend yield	0.00%	0.00%	0.00%

StockBased_Compensation_Schedu2

Stock-Based Compensation - Schedule of ESPP Granted Black Scholes (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Expected term (in years)	4 years 5 months	4 years 6 months 4 days	4 years 2 months 12 days
Risk-free interest rate	0.80%	0.80%	0.60%
Expected volatility	40.40%	44.40%	50.80%
Dividend yield	0.00%	0.00%	0.00%
ESPP
Expected term (in years)	6 months	6 months	6 months
Risk-free interest rate	0.10%	0.10%	0.10%
Expected volatility	33.50%	42.00%	51.00%
Dividend yield	0.00%	0.00%	0.00%

StockBased_Compensation_Schedu3

Stock-Based Compensation - Schedule of Summary of Stock Option Activity (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Shares (in thousands)
Outstanding at January 1, 2014	4,458
Granted	352
Exercised	-1,978
Forfeited	-161
Outstanding at December 31, 2014	2,671
Exercisable at December 31, 2014	1,933
Vested or expected to vest December 31, 2014	2,662
Weighted Average Exercise Price (in dollars per share)
Outstanding at January 1, 2014	$30.67
Granted	$12.73
Exercised	$28.87
Forfeited	$47.02
Outstanding at December 31, 2014	$28.65
Exercisable at December 31, 2014	$28.66
Vested or expected to vest December 31, 2014	$28.52
Weighted Average Remaining Contractual Term & Aggregate Intrinsic Value
Outstanding at December 31, 2014	3 years 5 months 22 days
Exercisable at December 31, 2014	2 years 8 months 5 days
Vested or expected to vest December 31, 2014	3 years 5 months 12 days
Outstanding at December 31, 2014	$168,706
Exercisable at December 31, 2014	121,722
Vested or expected to vest December 31, 2014	$167,600

StockBased_Compensation_Schedu4

Stock-Based Compensation - Schedule of Restricted Stock Units by Type (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Total restricted stock units vesting conditions granted	2,524	3,098	3,151
Service-based restricted stock units
Restricted stock units vesting conditions granted	1,949	2,338	2,782
Performance-based restricted stock units
Restricted stock units granted with performance based vesting	575	760	369

StockBased_Compensation_Schedu5

Stock-Based Compensation - Schedule of Deferred Stock Units Activity (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Deferred Stock Units
Units (in thousands)
Outstanding at January 1, 2014	238
Granted	48
Vested and distributed	-26
Outstanding at December 31, 2014	260
Weighted Average Grant Date Fair Value (in dollars per share)
Outstanding at January 1, 2014	$32.01
Granted	$54.06
Vested and distributed	$30.53
Outstanding at December 31, 2014	$36.35
Restricted Stock Units (RSUs)
Units (in thousands)
Outstanding at January 1, 2014	5,538
Granted	2,524
Vested and distributed	-2,504
Forfeited	-1,016
Outstanding at December 31, 2014	4,542
Weighted Average Grant Date Fair Value (in dollars per share)
Outstanding at January 1, 2014	$36.43
Granted	$59.72
Vested and distributed	$34.70
Forfeited	$42.20
Outstanding at December 31, 2014	$48.98

Income_Taxes_Narrative_Details

Income Taxes - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Deferred tax assets, valuation allowance	$1,222,000	$1,251,000
Change in deferred tax asset valuation allowance	-100,000
Undistributed foreign earnings	224,000,000
Deferred income tax liability on undistributed foreign earnings	45,000,000
Income tax adjustment, expense increase (decrease)		3,600,000	5,300,000
Unrecognized tax benefits including accrued interest and penalties	41,100,000	30,600,000	26,900,000
Unrecognized tax benefits, income tax penalties and interest accrued	7,700,000	5,900,000	5,900,000
Income tax interest and penalties expense	1,800,000		1,200,000
Significant change in unrecognized tax benefits reasonably possible	4,300,000
Domestic country
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	26,100,000	30,700,000
Research and development tax credit carryforwards	30,500,000	10,000,000
State and local jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	45,000,000	59,000,000
Foreign country
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	300,000	2,400,000
Research and development tax credit carryforwards		$4,400,000

Income_Taxes_Components_of_Inc

Income Taxes - Components of Income Tax Schedule (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S.	$408,391	$365,821	$245,252
Foreign	71,385	53,733	76,339
Income before provision for income taxes	$479,776	$419,554	$321,591

Income_Taxes_Provision_for_Inc

Income Taxes - Provision for Income Tax Schedule (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current tax provision:
Federal	$153,471	$77,671	$94,423
State	4,978	8,034	10,046
Foreign	13,259	13,019	18,952
Deferred tax (benefit) provision:
Federal	-13,073	24,210	-582
State	-15,220	-1,106	-2,045
Foreign	2,442	1,869	-3,189
Change in valuation allowance	-29	2,370	-3
Total	$145,828	$126,067	$117,602

Income_Taxes_Schedule_of_Diffe

Income Taxes - Schedule of Difference Between Effective and Statutory (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S. federal income tax rate	35.00%	35.00%	35.00%
State taxes	2.30%	3.40%	3.50%
Nondeductible stock-based compensation	1.40%	0.80%	1.30%
U.S. federal and state research and development credits	-3.20%	-3.50%	-0.60%
Change in state tax rates	-0.30%	0.00%	-0.40%
Foreign earnings	-1.90%	-2.60%	-3.50%
Disallowed officer compensation	0.10%	0.10%	0.60%
Domestic production activities deduction	-2.20%	-4.30%	0.00%
Change in the deferred tax asset valuation allowance	0.00%	0.60%	0.00%
State software development activities	-2.40%	0.00%	0.00%
Other	1.60%	0.50%	0.70%
Effective income tax rate	30.40%	30.00%	36.60%

Income_Taxes_Schedule_of_Defer

Income Taxes - Schedule of Deferred Tax and Related Valuation Allowance (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]
Accrued bonus	$19,572	$14,266
Deferred revenue	9,536	5,691
Deferred rent	10,518	6,738
Stock-based compensation	27,538	30,125
Net operating losses	11,466	14,392
Tax credit carryforwards	18,066	11,107
Other	7,276	5,361
Deferred tax assets	103,972	87,680
Depreciation and amortization	-14,868	-15,607
Acquired intangible assets	-40,126	-19,530
Internal-use software development costs capitalized	-39,396	-31,970
Deferred tax liabilities	-94,390	-67,107
Valuation allowance	-1,222	-1,251
Net deferred tax assets	$8,360	$19,322

Income_Taxes_Unrecognized_Tax_

Income Taxes - Unrecognized Tax Benefits (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance at beginning of year	$24,651	$20,902	$12,496
Gross increases — tax positions of prior periods	12,925	2,878	12,173
Gross increases — current-period tax positions	2,106	2,834	2,251
Gross decreases — tax positions of prior periods	-6,362	-1,213	-6,018
Gross decreases — settlements	0	-750	0
Balance at end of year	$33,320	$24,651	$20,902

Net_Income_per_Share_Schedule_

Net Income per Share - Schedule of Components Used in Diluted and Basic Income Per Common Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income	$97,107	$91,155	$72,886	$72,800	$80,349	$79,756	$61,895	$71,487	$333,948	$293,487	$203,989
Denominator:
Shares used for basic net income per share (in shares)									178,279	178,196	177,900
Effect of dilutive securities:
Stock options (in shares)									1,221	1,622	2,182
RSUs and deferred stock units (in shares)									1,686	1,965	1,667
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)									181,186	181,783	181,749
Basic net income per share (in dollars per share)	$0.55	$0.51	$0.41	$0.41	$0.45	$0.45	$0.35	$0.40	$1.87	$1.65	$1.15
Diluted net income per share (in dollars per share)	$0.54	$0.50	$0.40	$0.40	$0.44	$0.44	$0.34	$0.39	$1.84	$1.61	$1.12

Net_Income_per_Share_Schedule_1

Net Income per Share - Schedule of Anti-Dilutive Securities (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	1,758	2,822	5,439
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	402	1,649	2,551
Service-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	786	188	1,154
Performance-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	570	985	1,734
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	0	0	0
Warrants related to issuance of convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from computation	0	0	0

Segment_and_Geographic_Informa1

Segment and Geographic Information - Narrative (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
									segment
Segment Reporting Information [Line Items]
Number of operating segments (in number of segments)									1
Property and equipment, net	$601,591				$450,287				$601,591	$450,287
Revenue	536,295	498,042	476,035	453,502	435,980	395,790	378,106	368,046	1,963,874	1,577,922	1,373,947
United States
Segment Reporting Information [Line Items]
Property and equipment, net	249,500				210,900				249,500	210,900
Foreign locations
Segment Reporting Information [Line Items]
Property and equipment, net	175,800				124,900				175,800	124,900
Revenue									$531,900	$432,600	$369,000
Sales | Geographic Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk, number of foreign countries (in number of countries)									0		0
Concentration risk, percentage (in percentage)									10.00%		10.00%

Quarterly_Financial_Results_un2

Quarterly Financial Results (unaudited) - Schedule of Quarterly Financial Results (unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$536,295	$498,042	$476,035	$453,502	$435,980	$395,790	$378,106	$368,046	$1,963,874	$1,577,922	$1,373,947
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	163,201	158,812	149,318	139,612	133,951	132,039	124,705	120,392	610,943	511,087	529,900
Net income	$97,107	$91,155	$72,886	$72,800	$80,349	$79,756	$61,895	$71,487	$333,948	$293,487	$203,989
Basic net income per share (in dollars per share)	$0.55	$0.51	$0.41	$0.41	$0.45	$0.45	$0.35	$0.40	$1.87	$1.65	$1.15
Diluted net income per share (in dollars per share)	$0.54	$0.50	$0.40	$0.40	$0.44	$0.44	$0.34	$0.39	$1.84	$1.61	$1.12