Akamai (AKAM) 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 07, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	AKAMAI TECHNOLOGIES INC
Entity Central Index Key	1,086,222
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		170,630,343

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 363,703	$ 313,382
Marketable securities	447,850	398,554
Accounts receivable, net of reserves of $1,311 and $1,281 at March 31, 2018, and December 31, 2017, respectively	484,617	461,457
Prepaid expenses and other current assets	163,556	172,853
Total current assets	1,459,726	1,346,246
Property and equipment, net	845,118	862,535
Marketable securities	512,270	567,592
Goodwill	1,498,906	1,498,688
Acquired intangible assets, net	193,228	201,259
Deferred income tax assets	44,490	36,231
Other assets	133,166	136,365
Total assets	4,686,904	4,648,916
Current liabilities:
Accounts payable	81,239	80,278
Accrued expenses	253,075	283,743
Deferred revenue	95,490	70,495
Current portion of convertible senior notes	668,745	0
Other current liabilities	32,046	22,178
Total current liabilities	1,130,595	456,694
Deferred revenue	7,049	6,062
Deferred income tax liabilities	17,675	17,823
Convertible senior notes	0	662,913
Other liabilities	145,328	142,955
Total liabilities	1,300,647	1,286,447
Commitments and contingencies (Note 9)
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; 170,841,758 and 169,893,324 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	1,708	1,699
Additional paid-in capital	4,098,218	4,073,362
Accumulated other comprehensive loss	(18,334)	(21,930)
Treasury stock, at cost, 293,619 shares at March 31, 2018, and no shares at December 31, 2017	(19,785)	0
Accumulated deficit	(675,550)	(690,662)
Total stockholders’ equity	3,386,257	3,362,469
Total liabilities and stockholders’ equity	$ 4,686,904	$ 4,648,916

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable reserve	$ 1,311	$ 1,281
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	170,841,758	169,893,324
Common stock, shares outstanding	170,841,758	169,893,324
Treasury stock, shares	293,619	0

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 668,724	$ 600,293
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	234,825	205,727
Research and development	65,065	52,162
Sales and marketing	122,553	114,492
General and administrative	154,385	115,009
Amortization of acquired intangible assets	8,431	7,569
Restructuring charges	14,908	0
Total costs and operating expenses	600,167	494,959
Income from operations	68,557	105,334
Interest income	3,965	4,624
Interest expense	(4,850)	(4,597)
Other income (expense), net	21	(684)
Income before provision for income taxes	67,693	104,677
Provision for income taxes	13,979	30,094
Net income	$ 53,714	$ 74,583
Net income per share:
Basic (in dollars per share)	$ 0.32	$ 0.43
Diluted (in dollars per share)	$ 0.31	$ 0.43
Shares used in per share calculations:
Basic (in shares)	170,116	173,158
Diluted (in shares)	172,004	175,171

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 53,714	$ 74,583
Other comprehensive income:
Foreign currency translation adjustments	6,282	9,927
Change in unrealized (loss) gain on investments, net of income tax benefit (provision) of $871 and $(488) for the three months ended March 31, 2018 and 2017, respectively	(2,686)	810
Other comprehensive income	3,596	10,737
Comprehensive income	$ 57,310	$ 85,320

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Change in unrealized (loss) gain on investments, net of income tax benefit (provision) of $871 and $(488) for the three months ended March 31, 2018 and 2017, respectively	$ 871	$ (488)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 53,714	$ 74,583
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	104,095	86,533
Stock-based compensation	44,686	38,986
(Benefit) provision for deferred income taxes	(7,814)	28,425
Amortization of debt discount and issuance costs	4,850	4,597
Restructuring-related software charges	2,818	0
Other non-cash reconciling items, net	4,379	(129)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(18,419)	(19,876)
Prepaid expenses and other current assets	(4,927)	(47,172)
Accounts payable and accrued expenses	(31,312)	(23,940)
Deferred revenue	25,243	10,043
Other current liabilities	13,701	3,516
Other non-current assets and liabilities	996	(12,948)
Net cash provided by operating activities	192,010	142,618
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(79)	(10)
Purchases of property and equipment	(51,584)	(45,224)
Capitalization of internal-use software development costs	(61,491)	(45,957)
Purchases of short- and long-term marketable securities	(73,352)	(92,306)
Proceeds from sales of short- and long-term marketable securities	16,196	180,257
Proceeds from maturities of short- and long-term marketable securities	59,540	143,881
Other non-current assets and liabilities	(715)	(335)
Net cash (used in) provided by investing activities	(111,485)	140,306
Cash flows from financing activities:
Proceeds related to the issuance of common stock under stock plans	22,738	17,530
Employee taxes paid related to net share settlement of stock-based awards	(29,714)	(33,921)
Repurchases of common stock	(19,785)	(72,467)
Other non-current assets and liabilities	(3,900)	0
Net cash used in financing activities	(30,661)	(88,858)
Effects of exchange rate changes on cash, cash equivalents and restricted cash	1,165	5,019
Net increase in cash, and cash equivalents and restricted cash	51,029	199,085
Cash, cash equivalents and restricted cash at beginning of period	314,429	324,626
Cash, cash equivalents and restricted cash at end of period	365,458	523,711
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received of $4,476 and $815 for the three months ended March 31, 2018 and 2017, respectively	18,313	41,133
Non-cash investing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	7,811	6,411
Capitalization of stock-based compensation	$ 18,555	$ 39,200

Consolidated Statements of Cas8

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Cash Flows [Abstract]
Income tax refund received	$ 4,476	$ 815
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	363,703	522,319
Restricted cash	1,755	1,392
Cash, cash equivalents and restricted cash	$ 365,458	$ 523,711

Nature of Business and Basis of

Nature of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Nature of Business and Basis of Presentation Akamai Technologies, Inc. (the “Company”) provides cloud services for delivering, optimizing and securing content and business applications over the Internet. The Company's globally-distributed platform comprises more than 200,000 servers across 130 countries. The Company was incorporated in Delaware in 1998 and is headquartered in Cambridge, Massachusetts. The Company currently operates in one industry segment: providing cloud services for delivering, optimizing and securing content and business applications over the Internet. The accompanying interim consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information. These financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in the accompanying financial statements. Certain information and footnote disclosures normally included in the Company’s annual audited consolidated financial statements and accompanying notes have been condensed in, or omitted from, these interim financial statements. Accordingly, the unaudited consolidated financial statements included herein should be read in conjunction with the audited consolidated financial statements and accompanying notes included in the Company’s annual report on Form 10-K for the year ended December 31, 2017 , filed with the Securities and Exchange Commission on March 1, 2018. The results of operations presented in this quarterly report on Form 10-Q are not necessarily indicative of the results of operations that may be expected for any future periods. In the opinion of management, these unaudited consolidated financial statements include all adjustments, consisting only of normal recurring adjustments, that are necessary for a fair statement of the results of all interim periods reported herein. Newly-Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step model for recognizing revenue from contracts with customers. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard can be adopted using one of two methods: retrospectively to each prior period presented or a modified retrospective application by recognizing a cumulative-effect adjustment as a component of equity as of the date of adoption. The Company adopted this new standard on a retrospective basis on January 1, 2018. The changes to the Company's revenue recognition approach under this new standard primarily impact the timing of recognizing revenue from a small number of licensed software customers. There is little impact on revenue recognized for the Company's core services. As a result of the change, the Company also began capitalizing certain commission and incentive payments. In November 2016, the FASB issued guidance that requires restricted cash to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The Company adopted this new standard on a retrospective basis on January 1, 2018. The following table details the changes to the consolidated balance sheet as of December 31, 2017 as a result of the retrospective adoption of the new revenue recognition standard (in thousands): As Previously Reported Revenue Recognition Standard Adjustments As Revised ASSETS Current assets: Accounts receivable $ 459,127 $ 2,330 $ 461,457 Prepaid expenses and other current assets 137,809 35,044 172,853 Total current assets 1,308,872 37,374 1,346,246 Deferred income tax assets 51,069 (14,838 ) 36,231 Other assets 112,829 23,536 136,365 Total assets 4,602,844 46,072 4,648,916 LIABILITIES AND STOCKHOLDERS' EQUITY Current liabilities: Deferred revenue $ 77,705 $ (7,210 ) $ 70,495 Total current liabilities 463,904 (7,210 ) 456,694 Deferred revenue 6,839 (777 ) 6,062 Deferred income tax liabilities 15,510 2,313 17,823 Total liabilities 1,292,121 (5,674 ) 1,286,447 Stockholders' equity: Accumulated deficit (742,408 ) 51,746 (690,662 ) Total stockholders' equity 3,310,723 51,746 3,362,469 Total liabilities and stockholders' equity 4,602,844 46,072 4,648,916 The following table details the changes to the consolidated statement of income for the three months ended March 31, 2017 as a result of the retrospective adoption of the new revenue recognition standard (in thousands, except per share data): As Previously Reported Revenue Recognition Standard Adjustments As Revised Revenue $ 609,237 $ (8,944 ) $ 600,293 Costs and operating expenses: Cost of revenue (exclusive of amortization of acquired intangible assets) 205,703 24 205,727 Sales and marketing 113,566 926 114,492 Total costs and operating expenses 494,009 950 494,959 Income from operations 115,228 (9,894 ) 105,334 Income before provision for income taxes 114,571 (9,894 ) 104,677 Provision for income taxes 33,641 (3,547 ) 30,094 Net income 80,930 (6,347 ) 74,583 Net income per share: Basic $ 0.47 $ (0.04 ) $ 0.43 Diluted $ 0.46 $ (0.04 ) $ 0.43 The statement of comprehensive income for the three months ended March 31, 2017 was also impacted by the adjustments to net income of $6.3 million . The following table details the changes to the consolidated statement of cash flows for the three months ended March 31, 2017 as a result of the retrospective adoption of the new revenue recognition and statement of cash flow standards (in thousands): As Previously Reported Revenue Recognition Standard Adjustments Cash Flow Standard Adjustments As Revised Cash flows from operating activities: Net income $ 80,930 $ (6,347 ) $ — $ 74,583 Adjustments to reconcile net income to net cash provided by operating activities: Provision for deferred income taxes 31,972 (3,547 ) — 28,425 Changes in operating assets and liabilities, net of effects of acquisitions: Accounts receivable (30,146 ) 10,270 — (19,876 ) Prepaid expenses and other current assets (47,065 ) (107 ) — (47,172 ) Deferred revenue 10,876 (833 ) — 10,043 Other non-current assets and liabilities (13,512 ) 564 — (12,948 ) Net cash provided by operating activities 142,618 — — 142,618 Cash flows from investing activities: Other non-current assets and liabilities (1,230 ) — 895 (335 ) Net cash provided by investing activities 139,411 — 895 140,306 Effects of exchange rate changes on cash, cash equivalents and restricted cash 4,979 — 40 5,019 Net increase in cash, and cash equivalents and restricted cash 198,150 — 935 199,085 Cash, cash equivalents and restricted cash at beginning of period 324,169 — 457 324,626 Cash, cash equivalents and restricted cash at end of period 522,319 — 1,392 523,711 In October 2016, the FASB issued guidance that requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The Company adopted this new standard on January 1, 2018 using the modified retrospective basis, recognizing a cumulative-effect adjustment as a component of equity as of the date of adoption. Upon adoption, the Company reclassified $11.6 million from prepaid and other current assets and $27.0 million from other assets to beginning retained earnings. In January 2017, the FASB issued guidance that changes the definition of a "business" to assist entities with evaluating whether transactions should be accounted for as transfers of assets or business combinations. The Company adopted this guidance on January 1, 2018 and will apply it prospectively to future transactions. The adoption of this new accounting guidance had no immediate impact on the Company's consolidated financial statements; however, it may result in a future transaction being recorded as a transfer of assets, whereas previously the Company may have concluded it was a business combination. Recent Accounting Pronouncements In February 2016, the FASB issued guidance that requires companies to present assets and liabilities arising from leases with terms greater than 12 months on the consolidated balance sheets. The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize right-of-use assets and lease liabilities on the balance sheet and requiring disclosure of key information about leasing arrangements. This will impact all leases, including leases for real estate and co-location facilities, among other arrangements currently under evaluation. The Company plans to adopt this standard in the first quarter of 2019 and expects to record significant right-of-use assets and lease liabilities on its consolidated balance sheets. The Company has formed a project team to assess the current state of accounting for leases, to understand the gaps between the current state and required future state and to implement the new processes, systems and controls required. To date, the Company has completed its gap analysis and selected a software tool to assist with the accounting for leases. The Company is in the process of selecting and finalizing its accounting policies and developing a data collection plan. The Company expects the adoption of this standard to require changes to its processes, systems and controls over financial reporting. In June 2016, the FASB issued guidance that introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new "expected loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. This guidance will be effective for the Company on January 1, 2020. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements.

Significant Accounting Policies

Significant Accounting Policies Update	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies Update	Significant Accounting Policies Update The Company's significant accounting policies are detailed in Note 2 of its annual report on Form 10-K for the year ended December 31, 2017. As a result of the FASB's updated guidance for revenue recognition and related changes, as described in Note 1, the following policies have been updated as of the Company's adoption date of January 1, 2018, with retrospective application to the historical periods presented. Revenue Recognition The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. Services included in the Company's contracts consist of its core services – the delivery of content, applications and software over the Internet – as well as security solutions and professional services. Revenue is recognized upon transfer of control of promised services in an amount that reflects the consideration the Company expects to receive in exchange for those services. The Company enters into contracts that may include various combinations of these services, which are generally capable of being distinct and accounted for as separate performance obligations. These contracts generally commit the customer to a minimum of monthly, quarterly or annual levels of usage and specify the rate at which the customer must pay for actual usage above the stated minimum. Based on the typical structure of the Company's contracts, which are generally for monthly recurring services that are essentially the same over time and have the same pattern of transfer to the customer, most performance obligations represent a promise to deliver a series of distinct services over time. The Company's contracts with customers sometimes include promises to deliver multiple services to a customer. Determining whether services are distinct performance obligations often requires the exercise of judgment by management. For example, advanced features that enhance a service and are highly interrelated are generally not considered distinct; rather, they are combined with the service they relate to into one performance obligation. Different determinations related to combining services into performance obligations could result in differences in the timing and amount of revenue recognized in a period. Generally, the transaction price in a contract is equal to the committed price stated in the contract, less any discounts or rebates. Because the Company's typical contracts represent a series of distinct services delivered over time with the same pattern of transfer to the customer, variable consideration such as usage or "bursting" over committed contract levels is allocated to the period to which it relates. The amount of consideration recognized for usage above contract minimums is limited to the amount the Company expects to be entitled to receive in exchange for providing the services. Once the transaction price has been determined, the Company allocates such price among all performance obligations in the contract on a relative standalone selling price (“SSP”) basis. Determination of SSP requires the exercise of judgment by management. SSP is based on observable inputs such as the price the Company charges for the service when sold separately, or the discounted list price per management’s approved price list. In cases where services are not sold separately or price list rates are not available, a cost-plus-margin approach or adjusted market approach is used to determine SSP. Most content delivery and security services represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by the Company. Accordingly, revenue for those services is recognized over time, generally ratably over the term of the arrangement due to consistent monthly traffic commitments that expire each period. Any bursting over given commitments is recognized in the period in which the traffic was served. For services that involve traffic consumption, revenue is recognized in an amount that reflects the level of traffic served to a customer in a given period. For custom arrangements, other methods may be used as a measure of progress towards completion of satisfying the performance obligations. Some of the Company's services are satisfied at a point in time, such as one-time professional services contracts, integration services and most license sales where the primary obligation is delivery of the license at the start of the term. In these cases, revenue is recognized at the point in time of delivery or satisfaction of the performance obligation. 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. Consideration payable to a customer is reviewed as part of the transaction price. If the payment to the customer does not represent payment for a distinct service, revenue is recognized only up to the net amount of consideration after customer payment obligations are considered. The Company may also resell the licenses or services of third parties. If the Company is acting as an agent in an arrangement with a customer to provide third party services, the transaction price reflects only the net amount to which the Company will be entitled, after accounting for payments made to the third party responsible for satisfying the performance obligation. Incremental Costs to Obtain a Contract with a Customer The Company capitalizes incremental costs associated with obtaining customer contracts, specifically certain commission and incentive payments. These costs are deferred on the Company's consolidated balance sheets and amortized over the expected life of the customer arrangement on a straight-line basis. Based on the nature of the Company's unique technology and services, and the rate at which the Company continually enhances and updates its technology, the expected life of the customer arrangement is determined to be approximately 2.5 years . Amortization is primarily included in sales and marketing expense in the consolidated statements of income. The current portion of deferred commission and incentive payments is included in prepaid expenses and other current assets and the long-term portion is included in other assets on the Company's consolidated balance sheets. Contract Liabilities Contract liabilities primarily represent payments received from customers for which the related performance obligations have not yet been satisfied. These balances consist of the unearned portion of monthly service fees and integration fees, and prepayments made by customers for future periods. The current and long-term portions of the Company's contract liabilities are included in deferred revenue in the respective sections of the Company's consolidated balance sheets.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following is a summary of available-for-sale marketable securities held as of March 31, 2018 and December 31, 2017 (in thousands): Gross Unrealized Classification on Balance Sheet Amortized Cost Gains Losses Aggregate Fair Value Short-Term Marketable Securities Long-Term Marketable Securities As of March 31, 2018 Commercial paper $ 5,707 $ — $ (17 ) $ 5,690 $ 5,690 $ — Corporate bonds 734,080 — (7,253 ) 726,827 301,960 424,867 U.S. government agency obligations 219,515 — (1,887 ) 217,628 140,145 77,483 $ 959,302 $ — $ (9,157 ) $ 950,145 $ 447,795 $ 502,350 As of December 31, 2017 Commercial paper $ 6,951 $ — $ (9 ) $ 6,942 $ 6,942 $ — Corporate bonds 736,902 2 (3,829 ) 733,075 289,378 443,697 U.S. government agency obligations 220,014 — (1,764 ) 218,250 102,234 116,016 $ 963,867 $ 2 $ (5,602 ) $ 958,267 $ 398,554 $ 559,713 The Company offers certain eligible employees the ability to participate in a non-qualified deferred compensation plan. The mutual funds held by the Company that are associated with this plan are classified as restricted trading securities. These securities are not included in the available-for-sale securities table above but are included in marketable securities in the consolidated balance sheets. Unrealized gains and unrealized temporary losses on investments classified as available-for-sale are included within accumulated other comprehensive loss in the consolidated balance sheets. Upon realization, those amounts are reclassified from accumulated other comprehensive loss to interest income in the consolidated statements of income. As of March 31, 2018 , the Company held for investment corporate bonds with a fair value of $558.7 million , which are classified as available-for-sale marketable securities and have been in a continuous unrealized loss position for more than 12 months. The unrealized losses of $4.9 million related to these corporate bonds are included in accumulated other comprehensive income as of March 31, 2018 . The unrealized losses are attributable to changes in interest rates. Based on the evaluation of available evidence, the Company does not believe any unrealized losses represent other than temporary impairments. The following table details the fair value measurements within the fair value hierarchy of the Company’s financial assets and liabilities as of March 31, 2018 and December 31, 2017 (in thousands): Total Fair Value Fair Value Measurements at Reporting Date Using Level 1 Level 2 Level 3 As of March 31, 2018 Cash Equivalents and Marketable Securities: Money market funds $ 7,059 $ 7,059 $ — $ — Commercial paper 5,690 — 5,690 — Corporate bonds 726,827 — 726,827 — U.S. government agency obligations 217,628 — 217,628 — Mutual funds 9,975 9,975 — — $ 967,179 $ 17,034 $ 950,145 $ — Liabilities: Contingent consideration related to a completed acquisition $ (5,600 ) $ — $ — $ (5,600 ) As of December 31, 2017 Cash Equivalents and Marketable Securities: Money market funds $ 22,649 $ 22,649 $ — $ — Commercial paper 10,928 — 10,928 — Corporate bonds 733,075 — 733,075 — U.S. government agency obligations 218,248 — 218,248 — Mutual funds 7,879 7,879 — — $ 992,779 $ 30,528 $ 962,251 $ — Liabilities: Contingent consideration related to a completed acquisition $ (8,631 ) $ — $ — $ (8,631 ) As of March 31, 2018 and December 31, 2017 , the Company grouped money market funds and mutual funds using a Level 1 valuation because market prices for such investments are readily available in active markets. As of March 31, 2018 and December 31, 2017 , the Company grouped commercial paper, corporate bonds and U.S. government agency obligations 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 between Level 1, Level 2 or Level 3 of the fair value measurement hierarchy during the three months ended March 31, 2018 . When developing fair value estimates, the Company maximizes the use of observable inputs and minimizes the use of unobservable inputs. When available, the Company uses quoted market prices to measure fair value. The valuation technique used to measure fair value for the Company's Level 1 and Level 2 assets is a market approach, using prices and other relevant information generated by market transactions involving identical or comparable assets. If market prices are not available, the fair value measurement is based on models that use primarily market-based parameters including yield curves, volatilities, credit ratings and currency rates. In certain cases where market rate assumptions are not available, the Company is required to make judgments about assumptions market participants would use to estimate the fair value of a financial instrument. The valuation technique used to measure fair value of the Company's Level 3 liabilities, which consist of contingent consideration related to the acquisition of Cyberfend, Inc. in 2016, was primarily an income-based approach. The significant unobservable input used in the fair value measurement of the contingent consideration was the likelihood of achieving certain post-closing financial results. Contractual maturities of the Company’s available-for-sale marketable securities held as of March 31, 2018 and December 31, 2017 were as follows (in thousands): March 31, December 31, Due in 1 year or less $ 447,795 $ 398,554 Due after 1 year through 3 years 502,350 559,713 $ 950,145 $ 958,267 The following table reflects the activity for the Company’s major classes of liabilities measured at fair value using Level 3 inputs during the three months ended March 31, 2018 (in thousands): Other Liabilities: Balance as of January 1, 2018 $ (8,631 ) Fair value adjustment to contingent consideration included in general and administrative expense (1,135 ) Cash paid upon achievement of milestone 4,166 Balance as of March 31, 2018 $ (5,600 )

Accounts Receivable

Accounts Receivable	3 Months Ended
	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Accounts Receivable	Accounts Receivable Net accounts receivable consisted of the following as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Trade accounts receivable $ 345,112 $ 320,001 Unbilled accounts receivable 140,816 142,737 Gross accounts receivable 485,928 462,738 Allowance for doubtful accounts and other reserves (1,311 ) (1,281 ) Accounts receivable, net $ 484,617 $ 461,457

Incremental Costs to Obtain a C

Incremental Costs to Obtain a Contract with a Customer	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Incremental Costs to Obtain a Contract with a Customer	Incremental Costs to Obtain a Contract with a Customer The following table summarizes the deferred costs associated with obtaining customer contracts, specifically commission and incentive payments, as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Deferred costs included in prepaid and other current assets $ 34,786 $ 35,044 Deferred costs included in other assets 21,312 23,536 Total deferred costs $ 56,098 $ 58,580 During the three months ended March 31, 2018 and 2017, the Company recognized $10.9 million and $9.1 million , respectively, of amortization expense related to deferred commissions, which is primarily included in sales and marketing expense in the consolidated statements of income. Revenue from Contracts with Customers The Company sells its services 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. Other than the U.S., no single country accounted for 10% or more of the Company’s total revenue for any reported period. The following table summarizes revenue by geography included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended March 31, 2018 2017 U.S. $ 423,339 $ 398,870 International 245,385 201,423 Total revenue $ 668,724 $ 600,293 While the Company sells its services through a geographically disbursed sales force, it manages its customer relationships in two divisions: the Web Division and the Media and Carrier Division. These divisions manage a portfolio of customers that predominately purchase solutions managed by the division; however, customers may purchase solutions managed by the other division as well. The following table summarizes revenue by division included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended 2018 2017 Web Division $ 352,837 $ 303,488 Media and Carrier Division 315,887 296,805 Total revenue $ 668,724 $ 600,293 Most content delivery and security services represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by the Company. Accordingly, the majority of the Company's revenue is recognized over time, generally ratably over the term of the arrangement due to consistent monthly traffic commitments that expire each period. A small percentage of the Company's services are satisfied at a point in time, such as one-time professional services contracts, integration services and most license sales where the primary obligation is delivery of the license at the start of the term. In these cases, revenue is recognized at a point in time of delivery or satisfaction of the performance obligation. During the three months ended March 31, 2018 and 2017, the Company recognized $46.4 million and $31.0 million of revenue that was included in deferred revenue as of December 31, 2017 and 2016, respectively. As of March 31, 2018, the aggregate amount of remaining performance obligations from contracts with customers was $2.3 billion . The Company expects to recognize more than 70% of its remaining performance obligations as revenue over the next 12 months, with the remaining recognized thereafter. Remaining performance obligations represent the amount of the transaction price within contracts with customers that relates to performance obligations that are unsatisfied or partially satisfied at the reporting date. This consists of future committed revenue for monthly, quarterly or annual periods within current contracts with customers, as well as deferred revenue arising from consideration invoiced in prior periods for which the related performance obligation has not been satisfied. It excludes estimates of variable consideration such as usage-based contracts with no committed contract as well as anticipated renewed contracts.

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Intangible Assets	Goodwill and Acquired Intangible Assets The change in the carrying amount of goodwill for the three months ended March 31, 2018 was as follows (in thousands): Balance as of January 1, 2018 $ 1,498,688 Measurement period adjustments (2,263 ) Foreign currency translation 2,481 Balance as of March 31, 2018 $ 1,498,906 The Company tests goodwill for impairment at least annually. Through the date the consolidated financial statements were issued, no triggering events had occurred that would indicate a potential impairment exists. Acquired intangible assets that are subject to amortization consisted of the following as of March 31, 2018 and December 31, 2017 (in thousands): March 31, 2018 December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Accumulated Net Completed technology $ 145,091 $ (69,359 ) $ 75,732 $ 145,091 $ (65,283 ) $ 79,808 Customer-related intangible assets 245,710 (132,823 ) 112,887 245,310 (128,835 ) 116,475 Non-compete agreements 710 (163 ) 547 4,710 (3,975 ) 735 Trademarks and trade names 7,200 (3,138 ) 4,062 7,200 (2,959 ) 4,241 Acquired license rights 490 (490 ) — 490 (490 ) — Total $ 399,201 $ (205,973 ) $ 193,228 $ 402,801 $ (201,542 ) $ 201,259 Aggregate expense related to amortization of acquired intangible assets for the three months ended March 31, 2018 and 2017 was $8.4 million and $7.6 million , respectively. Based on the Company’s acquired intangible assets as of March 31, 2018 , aggregate expense related to amortization of acquired intangible assets is expected to be $24.9 million for the remainder of 2018 , and $36.6 million , $33.9 million , $28.0 million and $22.4 million for 2019 , 2020 , 2021 and 2022 , respectively.

Convertible Senior Notes

Convertible Senior Notes	3 Months Ended
	Mar. 31, 2018
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; or • during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the conversion rate on each such trading day; or upon the occurrence of specified corporate events. On or after August 15, 2018 , holders may convert all or any portion of their Notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date, regardless of the foregoing circumstances. Upon conversion, the Company, at its election, may pay or deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock. The initial conversion rate is 11.1651 shares of the Company's common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $89.56 per share, subject to adjustments in certain events, and represents a potential conversion into 7.7 million shares. In accounting for the issuance of the Notes, the Company separated the Notes into liability and equity components. The carrying cost of the liability component was calculated by measuring the fair value of a similar debt obligation that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the Notes. The difference between the principal amount of the Notes and the proceeds allocated to the liability component (“debt discount”) is amortized to interest expense using the effective interest method over the term of the Notes. The equity component is recorded in additional paid-in capital in the consolidated balance sheet and will not be remeasured as long as it continues to meet the conditions for equity classification. In accounting for the transaction costs related to the issuance of the Notes, the Company allocated the total transaction costs incurred to the liability and equity components based on their relative values. Transaction costs attributable to the liability component are being amortized to interest expense over the term of the Notes, and transaction costs attributable to the equity component are netted against the equity component of the Notes in stockholders’ equity. The Notes consist of the following components as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, 2017 Liability component: Principal $ 690,000 $ 690,000 Less: debt discount and issuance costs, net of amortization (21,255 ) (27,087 ) Net carrying amount $ 668,745 $ 662,913 Equity component: $ 101,276 $ 101,276 The estimated fair value of the Notes at March 31, 2018 was $712.9 million . The fair value was determined based on the quoted price of the Notes in an inactive market on the last trading day of the reporting period and has been classified as Level 2 within the fair value hierarchy. Based on the closing price of the Company's common stock of $70.98 on March 31, 2018 , the value of the Notes if converted to common stock was less than the principal amount of $690.0 million . The Company used $62.0 million of the proceeds from the offering to repurchase shares of its common stock, concurrent with the issuance of the Notes. The repurchase was made in accordance with a share repurchase program previously approved by the Board of Directors. Additionally, $23.3 million of the proceeds was used for the net cost of convertible note hedge and warrant transactions. The remaining net proceeds are for working capital, share repurchases and other general corporate purposes, as well as for potential acquisitions and strategic transactions. Note Hedge To minimize the impact of potential dilution upon conversion of the Notes, the Company entered into convertible note hedge transactions with respect to its common stock in February 2014. The Company paid $101.3 million for the note hedge transactions. The note hedge transactions cover approximately 7.7 million shares of the Company’s common stock at a strike price that corresponds to the initial conversion price of the Notes, also subject to adjustment, and are exercisable upon conversion of the Notes. The note hedge transactions are intended to reduce dilution in the event of conversion of the Notes. Warrants Separately, in February 2014, the Company entered into warrant transactions, whereby the Company sold warrants to acquire, subject to anti-dilution adjustments, up to 7.7 million shares of the Company’s common stock at a strike price of approximately $104.49 per share. The Company received aggregate proceeds of $78.0 million from the sale of the warrants. The convertible note hedge and warrant transactions will generally have the effect of increasing the conversion price of the Notes to approximately $104.49 per share. Interest Expense The Notes do not bear regular interest, but have an effective interest rate of 3.2% attributable to the conversion feature. The following table sets forth total interest expense included in the consolidated statements of income related to the Notes for the three months ended March 31, 2018 and 2017 (in thousands): For the Three Months 2018 2017 Amortization of debt discount and issuance costs $ 5,832 $ 5,632 Capitalization of interest expense (982 ) (1,035 ) Total interest expense $ 4,850 $ 4,597

Restructuring

Restructuring	3 Months Ended
	Mar. 31, 2018
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring During the fourth quarter of 2017, management committed to an action to restructure certain parts of the Company, with the intent of shifting focus to more critical areas of the business and away from products that have not seen expected commercial success. The restructuring is also intended to facilitate cost efficiencies and savings. As part of the cost efficiency and savings plans, certain headcount and facility reductions were made in 2017 and the first quarter of 2018. Certain capitalized internal-use software charges have also been realized for software not yet placed into service that will not be completed and implemented due to this action. The Company has incurred $62.4 million of restructuring charges as part of this action, of which $13.1 million was recognized during the three months ended March 31, 2018 and $49.3 million was recognized during the three months ended December 31, 2017. The Company expects to record additional restructuring charges in the remainder of 2018, primarily related to consolidating facilities. The Company does not expect the incremental charges to be material. The Company also recognized restructuring charges for redundant employees, facilities and contracts associated with acquisitions completed in 2017. The following table summarizes the activity of the Company's restructuring accrual during the three months ended March 31, 2018 (in thousands): Employee Severance and Related Benefits Software Charges Excess Facilities, Contract Terminations and Other Total Balance as of January 1, 2018 $ 12,857 $ — $ 1,386 $ 14,243 Costs incurred 7,163 2,818 4,927 14,908 Cash disbursements (10,766 ) — (2,986 ) (13,752 ) Software and other non-cash charges — (2,818 ) (1,787 ) (4,605 ) Balance as of March 31, 2018 $ 9,254 $ — $ 1,540 $ 10,794

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Matters In April 2018, as part of the resolution of multiple existing lawsuits between Limelight Networks, Inc. ("Limelight") and the Company, including in the U.S. District Court for the Eastern District of Virginia and in the U.S. District Court for the District of Massachusetts, the Company and Limelight entered into an agreement to settle the cases and request that the U.S. Patent Trial and Appeal Board terminate certain proceedings related to patents at issue in the litigation. The Company recorded a $14.9 million charge, which is included in general and administrative expenses in the consolidated statement of income, during the three months ended March 31, 2018 related to this settlement.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Share Repurchase Program In February 2016, the Board of Directors authorized a $1.0 billion repurchase program effective from February 2016 through December 2018. In March 2018, the Company announced that its Board had increased its share repurchase authorization by $416.7 million , such that the amount that is authorized and available for repurchase in 2018 is $750.0 million . The Company's goal for the share repurchase program is to return capital to shareholders, as business and market conditions warrant, and to offset the dilution created by its employee equity compensation programs. During the three months ended March 31, 2018 , the Company repurchased 0.3 million shares of its common stock for $19.8 million . Stock-Based Compensation The following table summarizes stock-based compensation included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): For the Three Months 2018 2017 Cost of revenue $ 5,296 $ 4,685 Research and development 10,509 9,029 Sales and marketing 15,959 15,157 General and administrative 12,922 10,115 Total stock-based compensation 44,686 38,986 Provision for income taxes (11,088 ) (17,985 ) Total stock-based compensation, net of income taxes $ 33,598 $ 21,001 In addition to the amounts of stock-based compensation reported in the table above, the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 include stock-based compensation reflected as a component of amortization of capitalized internal-use software of $5.6 million and $3.5 million , respectively, before taxes.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2018
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, net of tax, which is reported as a component of stockholders' equity, for the three months ended March 31, 2018 (in thousands): Foreign Currency Translation Net Unrealized Gains (Losses) on Investments Total Balance as of January 1, 2018 $ (24,319 ) $ 2,389 $ (21,930 ) Other comprehensive gain (loss) 6,282 (2,686 ) 3,596 Balance as of March 31, 2018 $ (18,037 ) $ (297 ) $ (18,334 ) Amounts reclassified from accumulated other comprehensive loss to net income were insignificant for the three months ended March 31, 2018 .

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Incremental Costs to Obtain a Contract with a Customer The following table summarizes the deferred costs associated with obtaining customer contracts, specifically commission and incentive payments, as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Deferred costs included in prepaid and other current assets $ 34,786 $ 35,044 Deferred costs included in other assets 21,312 23,536 Total deferred costs $ 56,098 $ 58,580 During the three months ended March 31, 2018 and 2017, the Company recognized $10.9 million and $9.1 million , respectively, of amortization expense related to deferred commissions, which is primarily included in sales and marketing expense in the consolidated statements of income. Revenue from Contracts with Customers The Company sells its services 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. Other than the U.S., no single country accounted for 10% or more of the Company’s total revenue for any reported period. The following table summarizes revenue by geography included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended March 31, 2018 2017 U.S. $ 423,339 $ 398,870 International 245,385 201,423 Total revenue $ 668,724 $ 600,293 While the Company sells its services through a geographically disbursed sales force, it manages its customer relationships in two divisions: the Web Division and the Media and Carrier Division. These divisions manage a portfolio of customers that predominately purchase solutions managed by the division; however, customers may purchase solutions managed by the other division as well. The following table summarizes revenue by division included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended 2018 2017 Web Division $ 352,837 $ 303,488 Media and Carrier Division 315,887 296,805 Total revenue $ 668,724 $ 600,293 Most content delivery and security services represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by the Company. Accordingly, the majority of the Company's revenue is recognized over time, generally ratably over the term of the arrangement due to consistent monthly traffic commitments that expire each period. A small percentage of the Company's services are satisfied at a point in time, such as one-time professional services contracts, integration services and most license sales where the primary obligation is delivery of the license at the start of the term. In these cases, revenue is recognized at a point in time of delivery or satisfaction of the performance obligation. During the three months ended March 31, 2018 and 2017, the Company recognized $46.4 million and $31.0 million of revenue that was included in deferred revenue as of December 31, 2017 and 2016, respectively. As of March 31, 2018, the aggregate amount of remaining performance obligations from contracts with customers was $2.3 billion . The Company expects to recognize more than 70% of its remaining performance obligations as revenue over the next 12 months, with the remaining recognized thereafter. Remaining performance obligations represent the amount of the transaction price within contracts with customers that relates to performance obligations that are unsatisfied or partially satisfied at the reporting date. This consists of future committed revenue for monthly, quarterly or annual periods within current contracts with customers, as well as deferred revenue arising from consideration invoiced in prior periods for which the related performance obligation has not been satisfied. It excludes estimates of variable consideration such as usage-based contracts with no committed contract as well as anticipated renewed contracts.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rate is based on estimated income for the year, the estimated composition of the income in different jurisdictions and discrete adjustments, if any, in the applicable quarterly periods. Potential discrete adjustments include tax charges or benefits related to stock-based compensation, changes in tax legislation, settlements of tax audits or assessments, uncertain tax positions and acquisitions, among other items. The Company’s effective income tax rate was 20.7% and 28.7% for the three months ended March 31, 2018 and 2017, respectively. The lower effective tax rate for the three months ended March 31, 2018, is primarily due to a reduction in the U.S. federal statutory tax rate from 35.0% to 21.0% as part of the U.S. Tax Cuts and Jobs Act (the "TCJA") that was enacted in December 2017. For the three months ended March 31, 2018, the effective income tax rate was lower than the federal statutory tax rate due to foreign income taxed at lower rates and the benefit of U.S. federal, state and foreign research and development credits, partially offset by U.S. federal taxes on Global Intangible Low-Taxed Income (“GILTI”) enacted as part of the TCJA and an intercompany sale of intellectual property. For the three months ended March 31, 2017, the effective income tax rate was lower than the federal statutory tax rate due to foreign income taxed at lower rates and the benefit of U.S. federal, state and foreign research and development credits, partially offset by the effects of accounting for stock-based compensation in accordance with the authoritative guidance for share-based payments and state income taxes. As of March 31, 2018, no changes have been made to the previously recorded provisional amounts related to the one-time transition tax and the re-measurement of the Company's deferred tax balances in its consolidated financial statements for the year ended December 31, 2017 due to the TCJA. Any changes to the provisional amounts will be recorded in the period in which the adjustments are made. These changes could arise from additional analysis, changes in assumptions or interpretations the Company has made, additional guidance that may be issued and actions the Company may take as a result of the TCJA. Beginning in 2018, the TCJA provides for a modified territorial tax system imposing an incremental tax on foreign income deemed to be taxed at a “low rate” (the aforementioned GILTI provisions). Under GAAP, an election must be made to either (1) treat taxes due related to GILTI as a current-period expense when incurred (the “period cost method”) or (2) factor such amounts into the measurement of deferred taxes (the “deferred method”). The Company is evaluating the effects of these provisions and has not yet adopted a policy to account for the related impacts.

Net Income per Share

Net Income per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share Reconciliation [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, restricted stock units ("RSUs"), deferred stock units ("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 three months ended March 31, 2018 and 2017 (in thousands, except per share data): For the Three Months 2018 2017 Numerator: Net income $ 53,714 $ 74,583 Denominator: Shares used for basic net income per share 170,116 173,158 Effect of dilutive securities: Stock options 142 360 RSUs and DSUs 1,746 1,653 Convertible senior notes — — Warrants related to issuance of convertible senior notes — — Shares used for diluted net income per share 172,004 175,171 Basic net income per share $ 0.32 $ 0.43 Diluted net income per share $ 0.31 $ 0.43 For the three months ended March 31, 2018 and 2017 , certain potential outstanding shares from stock options, service-based RSUs, convertible notes and warrants were excluded from the computation of diluted net income per share because the effect of including these items was anti-dilutive. Additionally, certain performance-based RSUs were excluded from the computation of diluted net income per share because the underlying performance conditions for such RSUs had not been met as of these dates. The number of potentially outstanding shares excluded from the computation of diluted net income per share for the three months ended March 31, 2018 and 2017 are as follows (in thousands): For the Three Months 2018 2017 Stock options — 3 Service-based RSUs 2,815 2,681 Performance-based RSUs 1,529 1,253 Convertible senior notes 7,704 7,704 Warrants related to issuance of convertible senior notes 7,704 7,704 Total shares excluded from computation 19,752 19,345

Nature of Business and Basis 23

Nature of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Newly-Adopted and Recent Accounting Pronouncements	Newly-Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step model for recognizing revenue from contracts with customers. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard can be adopted using one of two methods: retrospectively to each prior period presented or a modified retrospective application by recognizing a cumulative-effect adjustment as a component of equity as of the date of adoption. The Company adopted this new standard on a retrospective basis on January 1, 2018. The changes to the Company's revenue recognition approach under this new standard primarily impact the timing of recognizing revenue from a small number of licensed software customers. There is little impact on revenue recognized for the Company's core services. As a result of the change, the Company also began capitalizing certain commission and incentive payments. In November 2016, the FASB issued guidance that requires restricted cash to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The Company adopted this new standard on a retrospective basis on January 1, 2018. The following table details the changes to the consolidated balance sheet as of December 31, 2017 as a result of the retrospective adoption of the new revenue recognition standard (in thousands): As Previously Reported Revenue Recognition Standard Adjustments As Revised ASSETS Current assets: Accounts receivable $ 459,127 $ 2,330 $ 461,457 Prepaid expenses and other current assets 137,809 35,044 172,853 Total current assets 1,308,872 37,374 1,346,246 Deferred income tax assets 51,069 (14,838 ) 36,231 Other assets 112,829 23,536 136,365 Total assets 4,602,844 46,072 4,648,916 LIABILITIES AND STOCKHOLDERS' EQUITY Current liabilities: Deferred revenue $ 77,705 $ (7,210 ) $ 70,495 Total current liabilities 463,904 (7,210 ) 456,694 Deferred revenue 6,839 (777 ) 6,062 Deferred income tax liabilities 15,510 2,313 17,823 Total liabilities 1,292,121 (5,674 ) 1,286,447 Stockholders' equity: Accumulated deficit (742,408 ) 51,746 (690,662 ) Total stockholders' equity 3,310,723 51,746 3,362,469 Total liabilities and stockholders' equity 4,602,844 46,072 4,648,916 The following table details the changes to the consolidated statement of income for the three months ended March 31, 2017 as a result of the retrospective adoption of the new revenue recognition standard (in thousands, except per share data): As Previously Reported Revenue Recognition Standard Adjustments As Revised Revenue $ 609,237 $ (8,944 ) $ 600,293 Costs and operating expenses: Cost of revenue (exclusive of amortization of acquired intangible assets) 205,703 24 205,727 Sales and marketing 113,566 926 114,492 Total costs and operating expenses 494,009 950 494,959 Income from operations 115,228 (9,894 ) 105,334 Income before provision for income taxes 114,571 (9,894 ) 104,677 Provision for income taxes 33,641 (3,547 ) 30,094 Net income 80,930 (6,347 ) 74,583 Net income per share: Basic $ 0.47 $ (0.04 ) $ 0.43 Diluted $ 0.46 $ (0.04 ) $ 0.43 The statement of comprehensive income for the three months ended March 31, 2017 was also impacted by the adjustments to net income of $6.3 million . The following table details the changes to the consolidated statement of cash flows for the three months ended March 31, 2017 as a result of the retrospective adoption of the new revenue recognition and statement of cash flow standards (in thousands): As Previously Reported Revenue Recognition Standard Adjustments Cash Flow Standard Adjustments As Revised Cash flows from operating activities: Net income $ 80,930 $ (6,347 ) $ — $ 74,583 Adjustments to reconcile net income to net cash provided by operating activities: Provision for deferred income taxes 31,972 (3,547 ) — 28,425 Changes in operating assets and liabilities, net of effects of acquisitions: Accounts receivable (30,146 ) 10,270 — (19,876 ) Prepaid expenses and other current assets (47,065 ) (107 ) — (47,172 ) Deferred revenue 10,876 (833 ) — 10,043 Other non-current assets and liabilities (13,512 ) 564 — (12,948 ) Net cash provided by operating activities 142,618 — — 142,618 Cash flows from investing activities: Other non-current assets and liabilities (1,230 ) — 895 (335 ) Net cash provided by investing activities 139,411 — 895 140,306 Effects of exchange rate changes on cash, cash equivalents and restricted cash 4,979 — 40 5,019 Net increase in cash, and cash equivalents and restricted cash 198,150 — 935 199,085 Cash, cash equivalents and restricted cash at beginning of period 324,169 — 457 324,626 Cash, cash equivalents and restricted cash at end of period 522,319 — 1,392 523,711 In October 2016, the FASB issued guidance that requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The Company adopted this new standard on January 1, 2018 using the modified retrospective basis, recognizing a cumulative-effect adjustment as a component of equity as of the date of adoption. Upon adoption, the Company reclassified $11.6 million from prepaid and other current assets and $27.0 million from other assets to beginning retained earnings. In January 2017, the FASB issued guidance that changes the definition of a "business" to assist entities with evaluating whether transactions should be accounted for as transfers of assets or business combinations. The Company adopted this guidance on January 1, 2018 and will apply it prospectively to future transactions. The adoption of this new accounting guidance had no immediate impact on the Company's consolidated financial statements; however, it may result in a future transaction being recorded as a transfer of assets, whereas previously the Company may have concluded it was a business combination. Recent Accounting Pronouncements In February 2016, the FASB issued guidance that requires companies to present assets and liabilities arising from leases with terms greater than 12 months on the consolidated balance sheets. The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize right-of-use assets and lease liabilities on the balance sheet and requiring disclosure of key information about leasing arrangements. This will impact all leases, including leases for real estate and co-location facilities, among other arrangements currently under evaluation. The Company plans to adopt this standard in the first quarter of 2019 and expects to record significant right-of-use assets and lease liabilities on its consolidated balance sheets. The Company has formed a project team to assess the current state of accounting for leases, to understand the gaps between the current state and required future state and to implement the new processes, systems and controls required. To date, the Company has completed its gap analysis and selected a software tool to assist with the accounting for leases. The Company is in the process of selecting and finalizing its accounting policies and developing a data collection plan. The Company expects the adoption of this standard to require changes to its processes, systems and controls over financial reporting. In June 2016, the FASB issued guidance that introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new "expected loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. This guidance will be effective for the Company on January 1, 2020. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements.
Revenue Recognition, Incremental Costs to Obtain a Contract with a Customer and Contract Liabilities	Revenue Recognition The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. Services included in the Company's contracts consist of its core services – the delivery of content, applications and software over the Internet – as well as security solutions and professional services. Revenue is recognized upon transfer of control of promised services in an amount that reflects the consideration the Company expects to receive in exchange for those services. The Company enters into contracts that may include various combinations of these services, which are generally capable of being distinct and accounted for as separate performance obligations. These contracts generally commit the customer to a minimum of monthly, quarterly or annual levels of usage and specify the rate at which the customer must pay for actual usage above the stated minimum. Based on the typical structure of the Company's contracts, which are generally for monthly recurring services that are essentially the same over time and have the same pattern of transfer to the customer, most performance obligations represent a promise to deliver a series of distinct services over time. The Company's contracts with customers sometimes include promises to deliver multiple services to a customer. Determining whether services are distinct performance obligations often requires the exercise of judgment by management. For example, advanced features that enhance a service and are highly interrelated are generally not considered distinct; rather, they are combined with the service they relate to into one performance obligation. Different determinations related to combining services into performance obligations could result in differences in the timing and amount of revenue recognized in a period. Generally, the transaction price in a contract is equal to the committed price stated in the contract, less any discounts or rebates. Because the Company's typical contracts represent a series of distinct services delivered over time with the same pattern of transfer to the customer, variable consideration such as usage or "bursting" over committed contract levels is allocated to the period to which it relates. The amount of consideration recognized for usage above contract minimums is limited to the amount the Company expects to be entitled to receive in exchange for providing the services. Once the transaction price has been determined, the Company allocates such price among all performance obligations in the contract on a relative standalone selling price (“SSP”) basis. Determination of SSP requires the exercise of judgment by management. SSP is based on observable inputs such as the price the Company charges for the service when sold separately, or the discounted list price per management’s approved price list. In cases where services are not sold separately or price list rates are not available, a cost-plus-margin approach or adjusted market approach is used to determine SSP. Most content delivery and security services represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by the Company. Accordingly, revenue for those services is recognized over time, generally ratably over the term of the arrangement due to consistent monthly traffic commitments that expire each period. Any bursting over given commitments is recognized in the period in which the traffic was served. For services that involve traffic consumption, revenue is recognized in an amount that reflects the level of traffic served to a customer in a given period. For custom arrangements, other methods may be used as a measure of progress towards completion of satisfying the performance obligations. Some of the Company's services are satisfied at a point in time, such as one-time professional services contracts, integration services and most license sales where the primary obligation is delivery of the license at the start of the term. In these cases, revenue is recognized at the point in time of delivery or satisfaction of the performance obligation. 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. Consideration payable to a customer is reviewed as part of the transaction price. If the payment to the customer does not represent payment for a distinct service, revenue is recognized only up to the net amount of consideration after customer payment obligations are considered. The Company may also resell the licenses or services of third parties. If the Company is acting as an agent in an arrangement with a customer to provide third party services, the transaction price reflects only the net amount to which the Company will be entitled, after accounting for payments made to the third party responsible for satisfying the performance obligation. Incremental Costs to Obtain a Contract with a Customer The Company capitalizes incremental costs associated with obtaining customer contracts, specifically certain commission and incentive payments. These costs are deferred on the Company's consolidated balance sheets and amortized over the expected life of the customer arrangement on a straight-line basis. Based on the nature of the Company's unique technology and services, and the rate at which the Company continually enhances and updates its technology, the expected life of the customer arrangement is determined to be approximately 2.5 years . Amortization is primarily included in sales and marketing expense in the consolidated statements of income. The current portion of deferred commission and incentive payments is included in prepaid expenses and other current assets and the long-term portion is included in other assets on the Company's consolidated balance sheets. Contract Liabilities Contract liabilities primarily represent payments received from customers for which the related performance obligations have not yet been satisfied. These balances consist of the unearned portion of monthly service fees and integration fees, and prepayments made by customers for future periods. The current and long-term portions of the Company's contract liabilities are included in deferred revenue in the respective sections of the Company's consolidated balance sheets.

Nature of Business and Basis 24

Nature of Business and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of newly-adopted accounting pronouncements	The following table details the changes to the consolidated balance sheet as of December 31, 2017 as a result of the retrospective adoption of the new revenue recognition standard (in thousands): As Previously Reported Revenue Recognition Standard Adjustments As Revised ASSETS Current assets: Accounts receivable $ 459,127 $ 2,330 $ 461,457 Prepaid expenses and other current assets 137,809 35,044 172,853 Total current assets 1,308,872 37,374 1,346,246 Deferred income tax assets 51,069 (14,838 ) 36,231 Other assets 112,829 23,536 136,365 Total assets 4,602,844 46,072 4,648,916 LIABILITIES AND STOCKHOLDERS' EQUITY Current liabilities: Deferred revenue $ 77,705 $ (7,210 ) $ 70,495 Total current liabilities 463,904 (7,210 ) 456,694 Deferred revenue 6,839 (777 ) 6,062 Deferred income tax liabilities 15,510 2,313 17,823 Total liabilities 1,292,121 (5,674 ) 1,286,447 Stockholders' equity: Accumulated deficit (742,408 ) 51,746 (690,662 ) Total stockholders' equity 3,310,723 51,746 3,362,469 Total liabilities and stockholders' equity 4,602,844 46,072 4,648,916 The following table details the changes to the consolidated statement of income for the three months ended March 31, 2017 as a result of the retrospective adoption of the new revenue recognition standard (in thousands, except per share data): As Previously Reported Revenue Recognition Standard Adjustments As Revised Revenue $ 609,237 $ (8,944 ) $ 600,293 Costs and operating expenses: Cost of revenue (exclusive of amortization of acquired intangible assets) 205,703 24 205,727 Sales and marketing 113,566 926 114,492 Total costs and operating expenses 494,009 950 494,959 Income from operations 115,228 (9,894 ) 105,334 Income before provision for income taxes 114,571 (9,894 ) 104,677 Provision for income taxes 33,641 (3,547 ) 30,094 Net income 80,930 (6,347 ) 74,583 Net income per share: Basic $ 0.47 $ (0.04 ) $ 0.43 Diluted $ 0.46 $ (0.04 ) $ 0.43 The statement of comprehensive income for the three months ended March 31, 2017 was also impacted by the adjustments to net income of $6.3 million . The following table details the changes to the consolidated statement of cash flows for the three months ended March 31, 2017 as a result of the retrospective adoption of the new revenue recognition and statement of cash flow standards (in thousands): As Previously Reported Revenue Recognition Standard Adjustments Cash Flow Standard Adjustments As Revised Cash flows from operating activities: Net income $ 80,930 $ (6,347 ) $ — $ 74,583 Adjustments to reconcile net income to net cash provided by operating activities: Provision for deferred income taxes 31,972 (3,547 ) — 28,425 Changes in operating assets and liabilities, net of effects of acquisitions: Accounts receivable (30,146 ) 10,270 — (19,876 ) Prepaid expenses and other current assets (47,065 ) (107 ) — (47,172 ) Deferred revenue 10,876 (833 ) — 10,043 Other non-current assets and liabilities (13,512 ) 564 — (12,948 ) Net cash provided by operating activities 142,618 — — 142,618 Cash flows from investing activities: Other non-current assets and liabilities (1,230 ) — 895 (335 ) Net cash provided by investing activities 139,411 — 895 140,306 Effects of exchange rate changes on cash, cash equivalents and restricted cash 4,979 — 40 5,019 Net increase in cash, and cash equivalents and restricted cash 198,150 — 935 199,085 Cash, cash equivalents and restricted cash at beginning of period 324,169 — 457 324,626 Cash, cash equivalents and restricted cash at end of period 522,319 — 1,392 523,711

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities	The following is a summary of available-for-sale marketable securities held as of March 31, 2018 and December 31, 2017 (in thousands): Gross Unrealized Classification on Balance Sheet Amortized Cost Gains Losses Aggregate Fair Value Short-Term Marketable Securities Long-Term Marketable Securities As of March 31, 2018 Commercial paper $ 5,707 $ — $ (17 ) $ 5,690 $ 5,690 $ — Corporate bonds 734,080 — (7,253 ) 726,827 301,960 424,867 U.S. government agency obligations 219,515 — (1,887 ) 217,628 140,145 77,483 $ 959,302 $ — $ (9,157 ) $ 950,145 $ 447,795 $ 502,350 As of December 31, 2017 Commercial paper $ 6,951 $ — $ (9 ) $ 6,942 $ 6,942 $ — Corporate bonds 736,902 2 (3,829 ) 733,075 289,378 443,697 U.S. government agency obligations 220,014 — (1,764 ) 218,250 102,234 116,016 $ 963,867 $ 2 $ (5,602 ) $ 958,267 $ 398,554 $ 559,713
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 March 31, 2018 and December 31, 2017 (in thousands): Total Fair Value Fair Value Measurements at Reporting Date Using Level 1 Level 2 Level 3 As of March 31, 2018 Cash Equivalents and Marketable Securities: Money market funds $ 7,059 $ 7,059 $ — $ — Commercial paper 5,690 — 5,690 — Corporate bonds 726,827 — 726,827 — U.S. government agency obligations 217,628 — 217,628 — Mutual funds 9,975 9,975 — — $ 967,179 $ 17,034 $ 950,145 $ — Liabilities: Contingent consideration related to a completed acquisition $ (5,600 ) $ — $ — $ (5,600 ) As of December 31, 2017 Cash Equivalents and Marketable Securities: Money market funds $ 22,649 $ 22,649 $ — $ — Commercial paper 10,928 — 10,928 — Corporate bonds 733,075 — 733,075 — U.S. government agency obligations 218,248 — 218,248 — Mutual funds 7,879 7,879 — — $ 992,779 $ 30,528 $ 962,251 $ — Liabilities: Contingent consideration related to a completed acquisition $ (8,631 ) $ — $ — $ (8,631 )
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 March 31, 2018 and December 31, 2017 were as follows (in thousands): March 31, December 31, Due in 1 year or less $ 447,795 $ 398,554 Due after 1 year through 3 years 502,350 559,713 $ 950,145 $ 958,267
Schedule of Activity of Major Classes of Assets Measured at Fair Value Using Level 3 Inputs	The following table reflects the activity for the Company’s major classes of liabilities measured at fair value using Level 3 inputs during the three months ended March 31, 2018 (in thousands): Other Liabilities: Balance as of January 1, 2018 $ (8,631 ) Fair value adjustment to contingent consideration included in general and administrative expense (1,135 ) Cash paid upon achievement of milestone 4,166 Balance as of March 31, 2018 $ (5,600 )

Accounts Receivable (Tables)

Accounts Receivable (Tables)	3 Months Ended
	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Schedule of Accounts Receivable	Net accounts receivable consisted of the following as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Trade accounts receivable $ 345,112 $ 320,001 Unbilled accounts receivable 140,816 142,737 Gross accounts receivable 485,928 462,738 Allowance for doubtful accounts and other reserves (1,311 ) (1,281 ) Accounts receivable, net $ 484,617 $ 461,457

Incremental Costs to Obtain a27

Incremental Costs to Obtain a Contract with a Customer (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of deferred costs associated with obtaining customer contracts	The following table summarizes the deferred costs associated with obtaining customer contracts, specifically commission and incentive payments, as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, Deferred costs included in prepaid and other current assets $ 34,786 $ 35,044 Deferred costs included in other assets 21,312 23,536 Total deferred costs $ 56,098 $ 58,580

Goodwill and Acquired Intangi28

Goodwill and Acquired Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The change in the carrying amount of goodwill for the three months ended March 31, 2018 was as follows (in thousands): Balance as of January 1, 2018 $ 1,498,688 Measurement period adjustments (2,263 ) Foreign currency translation 2,481 Balance as of March 31, 2018 $ 1,498,906
Schedule of Acquired Intangible Assets	Acquired intangible assets that are subject to amortization consisted of the following as of March 31, 2018 and December 31, 2017 (in thousands): March 31, 2018 December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Accumulated Net Completed technology $ 145,091 $ (69,359 ) $ 75,732 $ 145,091 $ (65,283 ) $ 79,808 Customer-related intangible assets 245,710 (132,823 ) 112,887 245,310 (128,835 ) 116,475 Non-compete agreements 710 (163 ) 547 4,710 (3,975 ) 735 Trademarks and trade names 7,200 (3,138 ) 4,062 7,200 (2,959 ) 4,241 Acquired license rights 490 (490 ) — 490 (490 ) — Total $ 399,201 $ (205,973 ) $ 193,228 $ 402,801 $ (201,542 ) $ 201,259

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Convertible Senior Notes	The Notes consist of the following components as of March 31, 2018 and December 31, 2017 (in thousands): March 31, December 31, 2017 Liability component: Principal $ 690,000 $ 690,000 Less: debt discount and issuance costs, net of amortization (21,255 ) (27,087 ) Net carrying amount $ 668,745 $ 662,913 Equity component: $ 101,276 $ 101,276
Schedule of Interest Expense	The following table sets forth total interest expense included in the consolidated statements of income related to the Notes for the three months ended March 31, 2018 and 2017 (in thousands): For the Three Months 2018 2017 Amortization of debt discount and issuance costs $ 5,832 $ 5,632 Capitalization of interest expense (982 ) (1,035 ) Total interest expense $ 4,850 $ 4,597

Restructuring (Tables)

Restructuring (Tables)	3 Months Ended
	Mar. 31, 2018
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Accrual	The following table summarizes the activity of the Company's restructuring accrual during the three months ended March 31, 2018 (in thousands): Employee Severance and Related Benefits Software Charges Excess Facilities, Contract Terminations and Other Total Balance as of January 1, 2018 $ 12,857 $ — $ 1,386 $ 14,243 Costs incurred 7,163 2,818 4,927 14,908 Cash disbursements (10,766 ) — (2,986 ) (13,752 ) Software and other non-cash charges — (2,818 ) (1,787 ) (4,605 ) Balance as of March 31, 2018 $ 9,254 $ — $ 1,540 $ 10,794

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Schedule of Stock-Based Compensation Expense	The following table summarizes stock-based compensation included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): For the Three Months 2018 2017 Cost of revenue $ 5,296 $ 4,685 Research and development 10,509 9,029 Sales and marketing 15,959 15,157 General and administrative 12,922 10,115 Total stock-based compensation 44,686 38,986 Provision for income taxes (11,088 ) (17,985 ) Total stock-based compensation, net of income taxes $ 33,598 $ 21,001

Accumulated Other Comprehensi32

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2018
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, net of tax, which is reported as a component of stockholders' equity, for the three months ended March 31, 2018 (in thousands): Foreign Currency Translation Net Unrealized Gains (Losses) on Investments Total Balance as of January 1, 2018 $ (24,319 ) $ 2,389 $ (21,930 ) Other comprehensive gain (loss) 6,282 (2,686 ) 3,596 Balance as of March 31, 2018 $ (18,037 ) $ (297 ) $ (18,334 )

Revenue from Contracts with C33

Revenue from Contracts with Customers (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table summarizes revenue by geography included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended March 31, 2018 2017 U.S. $ 423,339 $ 398,870 International 245,385 201,423 Total revenue $ 668,724 $ 600,293 The following table summarizes revenue by division included in the Company’s consolidated statements of income for the three months ended March 31, 2018 and 2017 (in thousands): Three Months Ended 2018 2017 Web Division $ 352,837 $ 303,488 Media and Carrier Division 315,887 296,805 Total revenue $ 668,724 $ 600,293

Net Income per Share (Tables)

Net Income per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share Reconciliation [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 three months ended March 31, 2018 and 2017 (in thousands, except per share data): For the Three Months 2018 2017 Numerator: Net income $ 53,714 $ 74,583 Denominator: Shares used for basic net income per share 170,116 173,158 Effect of dilutive securities: Stock options 142 360 RSUs and DSUs 1,746 1,653 Convertible senior notes — — Warrants related to issuance of convertible senior notes — — Shares used for diluted net income per share 172,004 175,171 Basic net income per share $ 0.32 $ 0.43 Diluted net income per share $ 0.31 $ 0.43
Schedule of Shares Excluded from Computation of Diluted Earnings Per Share	The number of potentially outstanding shares excluded from the computation of diluted net income per share for the three months ended March 31, 2018 and 2017 are as follows (in thousands): For the Three Months 2018 2017 Stock options — 3 Service-based RSUs 2,815 2,681 Performance-based RSUs 1,529 1,253 Convertible senior notes 7,704 7,704 Warrants related to issuance of convertible senior notes 7,704 7,704 Total shares excluded from computation 19,752 19,345

Nature of Business and Basis 35

Nature of Business and Basis of Presentation (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)segmentcountryserver$ / shares	Mar. 31, 2017USD ($)$ / shares	Dec. 31, 2017USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of servers (more than) | server	200,000
Number of countries in which servers are located | country	130
Number of industry segments | segment	1
Current assets:
Accounts receivable	$ 484,617		$ 461,457
Prepaid expenses and other current assets	163,556		172,853
Total current assets	1,459,726		1,346,246
Deferred income tax assets	44,490		36,231
Other assets	133,166		136,365
Total assets	4,686,904		4,648,916
Current liabilities:
Deferred revenue	95,490		70,495
Total current liabilities	1,130,595		456,694
Deferred revenue	7,049		6,062
Deferred income tax liabilities	17,675		17,823
Total liabilities	1,300,647		1,286,447
Stockholders’ equity:
Accumulated deficit	(675,550)		(690,662)
Total stockholders’ equity	3,386,257		3,362,469
Total liabilities and stockholders’ equity	4,686,904		4,648,916
Revenue	668,724	$ 600,293
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	234,825	205,727
Sales and marketing	122,553	114,492
Total costs and operating expenses	600,167	494,959
Income from operations	68,557	105,334
Income before provision for income taxes	67,693	104,677
Provision for income taxes	$ 13,979	$ 30,094
Net income per share:
Basic (in dollars per share) | $ / shares	$ 0.32	$ 0.43
Diluted (in dollars per share) | $ / shares	$ 0.31	$ 0.43
Comprehensive income	$ 57,310	$ 85,320
Cash flows from operating activities:
Net income	53,714	74,583
Adjustments to reconcile net income to net cash provided by operating activities:
(Benefit) provision for deferred income taxes	(7,814)	28,425
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(18,419)	(19,876)
Prepaid expenses and other current assets	(4,927)	(47,172)
Deferred revenue	25,243	10,043
Other non-current assets and liabilities	996	(12,948)
Net cash provided by operating activities	192,010	142,618
Cash flows from investing activities:
Other non-current assets and liabilities	(715)	(335)
Net cash (used in) provided by investing activities	(111,485)	140,306
Effects of exchange rate changes on cash, cash equivalents and restricted cash	1,165	5,019
Net increase in cash, and cash equivalents and restricted cash	51,029	199,085
Cash, cash equivalents and restricted cash at beginning of period	314,429	324,626
Cash, cash equivalents and restricted cash at end of period	$ 365,458	523,711
Prepaid and other current assets | Intra-Entity Asset Transfers
Cash flows from investing activities:
Cumulative-effect adjustment			11,600
Deferred costs included in other assets | Intra-Entity Asset Transfers
Cash flows from investing activities:
Cumulative-effect adjustment			27,000
As Previously Reported
Current assets:
Accounts receivable			459,127
Prepaid expenses and other current assets			137,809
Total current assets			1,308,872
Deferred income tax assets			51,069
Other assets			112,829
Total assets			4,602,844
Current liabilities:
Deferred revenue			77,705
Total current liabilities			463,904
Deferred revenue			6,839
Deferred income tax liabilities			15,510
Total liabilities			1,292,121
Stockholders’ equity:
Accumulated deficit			(742,408)
Total stockholders’ equity			3,310,723
Total liabilities and stockholders’ equity			4,602,844
Revenue		609,237
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)		205,703
Sales and marketing		113,566
Total costs and operating expenses		494,009
Income from operations		115,228
Income before provision for income taxes		114,571
Provision for income taxes		$ 33,641
Net income per share:
Basic (in dollars per share) | $ / shares		$ 0.47
Diluted (in dollars per share) | $ / shares		$ 0.46
Cash flows from operating activities:
Net income		$ 80,930
Adjustments to reconcile net income to net cash provided by operating activities:
(Benefit) provision for deferred income taxes		31,972
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable		(30,146)
Prepaid expenses and other current assets		(47,065)
Deferred revenue		10,876
Other non-current assets and liabilities		(13,512)
Net cash provided by operating activities		142,618
Cash flows from investing activities:
Other non-current assets and liabilities		(1,230)
Net cash (used in) provided by investing activities		139,411
Effects of exchange rate changes on cash, cash equivalents and restricted cash		4,979
Net increase in cash, and cash equivalents and restricted cash		198,150
Cash, cash equivalents and restricted cash at beginning of period		324,169
Cash, cash equivalents and restricted cash at end of period		522,319
Adjustments | Accounting Standards Update 2014-09
Current assets:
Accounts receivable			2,330
Prepaid expenses and other current assets			35,044
Total current assets			37,374
Deferred income tax assets			(14,838)
Other assets			23,536
Total assets			46,072
Current liabilities:
Deferred revenue			(7,210)
Total current liabilities			(7,210)
Deferred revenue			(777)
Deferred income tax liabilities			2,313
Total liabilities			(5,674)
Stockholders’ equity:
Accumulated deficit			51,746
Total stockholders’ equity			51,746
Total liabilities and stockholders’ equity			$ 46,072
Revenue		(8,944)
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)		24
Sales and marketing		926
Total costs and operating expenses		950
Income from operations		(9,894)
Income before provision for income taxes		(9,894)
Provision for income taxes		$ (3,547)
Net income per share:
Basic (in dollars per share) | $ / shares		$ (0.04)
Diluted (in dollars per share) | $ / shares		$ (0.04)
Comprehensive income		$ 6,300
Cash flows from operating activities:
Net income		(6,347)
Adjustments to reconcile net income to net cash provided by operating activities:
(Benefit) provision for deferred income taxes		(3,547)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable		10,270
Prepaid expenses and other current assets		(107)
Deferred revenue		(833)
Other non-current assets and liabilities		564
Net cash provided by operating activities		0
Cash flows from investing activities:
Other non-current assets and liabilities		0
Net cash (used in) provided by investing activities		0
Effects of exchange rate changes on cash, cash equivalents and restricted cash		0
Net increase in cash, and cash equivalents and restricted cash		0
Cash, cash equivalents and restricted cash at beginning of period		0
Cash, cash equivalents and restricted cash at end of period		0
Adjustments | Accounting Standards Update 2016-18
Cash flows from operating activities:
Net income		0
Adjustments to reconcile net income to net cash provided by operating activities:
(Benefit) provision for deferred income taxes		0
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable		0
Prepaid expenses and other current assets		0
Deferred revenue		0
Other non-current assets and liabilities		0
Net cash provided by operating activities		0
Cash flows from investing activities:
Other non-current assets and liabilities		895
Net cash (used in) provided by investing activities		895
Effects of exchange rate changes on cash, cash equivalents and restricted cash		40
Net increase in cash, and cash equivalents and restricted cash		935
Cash, cash equivalents and restricted cash at beginning of period		457
Cash, cash equivalents and restricted cash at end of period		$ 1,392

Significant Accounting Polici36

Significant Accounting Policies Update (Details)	3 Months Ended
	Mar. 31, 2018
Internally developed software
Property, Plant and Equipment [Line Items]
Useful life	2 years 6 months

Fair Value Measurements - Marke

Fair Value Measurements - Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 959,302	$ 963,867
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(9,157)	(5,602)
Aggregate Fair Value	950,145	958,267
Short-Term Marketable Securities	447,795	398,554
Long-Term Marketable Securities	502,350	559,713
Unrealized losses included in accumulated other comprehensive loss	558,700
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,707	6,951
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(17)	(9)
Aggregate Fair Value	5,690	6,942
Short-Term Marketable Securities	5,690	6,942
Long-Term Marketable Securities	0	0
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	734,080	736,902
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(7,253)	(3,829)
Aggregate Fair Value	726,827	733,075
Short-Term Marketable Securities	301,960	289,378
Long-Term Marketable Securities	424,867	443,697
Available-for-sale marketable securities, continuous unrealized loss position for more than 12 months	4,900
U.S. government agency obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	219,515	220,014
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,887)	(1,764)
Aggregate Fair Value	217,628	218,250
Short-Term Marketable Securities	140,145	102,234
Long-Term Marketable Securities	$ 77,483	$ 116,016

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value Measurement (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	$ 950,145	$ 958,267
Commercial paper
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	5,690	6,942
Corporate bonds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	726,827	733,075
U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	217,628	218,250
Level 1
Cash Equivalents and Marketable Securities:
Cash equivalents and marketable securities	17,034	30,528
Contingent consideration related to a completed acquisition	0	0
Level 1 | Money market funds
Cash Equivalents and Marketable Securities:
Money market funds	7,059	22,649
Level 1 | Commercial paper
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 1 | Corporate bonds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 1 | U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 1 | Mutual funds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	9,975	7,879
Level 2
Cash Equivalents and Marketable Securities:
Cash equivalents and marketable securities	950,145	962,251
Contingent consideration related to a completed acquisition	0	0
Level 2 | Money market funds
Cash Equivalents and Marketable Securities:
Money market funds	0	0
Level 2 | Commercial paper
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	5,690	10,928
Level 2 | Corporate bonds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	726,827	733,075
Level 2 | U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	217,628	218,248
Level 2 | Mutual funds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 3
Cash Equivalents and Marketable Securities:
Cash equivalents and marketable securities	0	0
Contingent consideration related to a completed acquisition	(5,600)	(8,631)
Level 3 | Money market funds
Cash Equivalents and Marketable Securities:
Money market funds	0	0
Level 3 | Commercial paper
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 3 | Corporate bonds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 3 | U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Level 3 | Mutual funds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	0	0
Total Fair Value
Cash Equivalents and Marketable Securities:
Cash equivalents and marketable securities	967,179	992,779
Contingent consideration related to a completed acquisition	(5,600)	(8,631)
Total Fair Value | Money market funds
Cash Equivalents and Marketable Securities:
Money market funds	7,059	22,649
Total Fair Value | Commercial paper
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	5,690	10,928
Total Fair Value | Corporate bonds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	726,827	733,075
Total Fair Value | U.S. government agency obligations
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	217,628	218,248
Total Fair Value | Mutual funds
Cash Equivalents and Marketable Securities:
Aggregate Fair Value	$ 9,975	$ 7,879

Fair Value Measurements - Contr

Fair Value Measurements - Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Due in 1 year or less	$ 447,795	$ 398,554
Due after 1 year through 3 years	502,350	559,713
Aggregate Fair Value	$ 950,145	$ 958,267

Fair Value Measurements - Sch40

Fair Value Measurements - Schedule of Liability Measured at Fair Value using Level 3 Inputs (Details) - Level 3 $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of January 1, 2018	$ (8,631)
Fair value adjustment to contingent consideration included in general and administrative expense	(1,135)
Cash paid upon achievement of milestone	4,166
Balance as of March 31, 2018	$ (5,600)

Accounts Receivable - Schedule

Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 485,928	$ 462,738
Allowance for doubtful accounts and other reserves	(1,311)	(1,281)
Accounts receivable, net	484,617	461,457
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	140,816	142,737
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 345,112	$ 320,001

Incremental Costs to Obtain a42

Incremental Costs to Obtain a Contract with a Customer (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Commission and incentive payments
Capitalized Contract Cost [Line Items]
Total deferred costs	$ 56,098		$ 58,580
Commission and incentive payments | Deferred costs included in prepaid and other current assets
Capitalized Contract Cost [Line Items]
Total deferred costs	34,786		35,044
Commission and incentive payments | Deferred costs included in other assets
Capitalized Contract Cost [Line Items]
Total deferred costs	21,312		$ 23,536
Deferred commissions
Capitalized Contract Cost [Line Items]
Amortization expense	$ 10,900	$ 9,100

Goodwill and Acquired Intangi43

Goodwill and Acquired Intangible Assets - Schedule of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Schedule of Goodwill [Roll Forward]
Balance as of January 1, 2018	$ 1,498,688
Measurement period adjustments	(2,263)
Foreign currency translation	2,481
Balance as of March 31, 2018	$ 1,498,906

Goodwill and Acquired Intangi44

Goodwill and Acquired Intangible Assets - Schedule of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 399,201	$ 402,801
Accumulated Amortization	(205,973)	(201,542)
Net Carrying Amount	193,228	201,259
Completed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	145,091	145,091
Accumulated Amortization	(69,359)	(65,283)
Net Carrying Amount	75,732	79,808
Customer-related intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	245,710	245,310
Accumulated Amortization	(132,823)	(128,835)
Net Carrying Amount	112,887	116,475
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	710	4,710
Accumulated Amortization	(163)	(3,975)
Net Carrying Amount	547	735
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,200	7,200
Accumulated Amortization	(3,138)	(2,959)
Net Carrying Amount	4,062	4,241
Acquired license rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	490	490
Accumulated Amortization	(490)	(490)
Net Carrying Amount	$ 0	$ 0

Goodwill and Acquired Intangi45

Goodwill and Acquired Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 8,431	$ 7,569
Future amortization expense to be recognized in remainder of 2018	24,900
Future amortization expense 2019	36,600
Future amortization expense 2020	33,900
Future amortization expense 2021	28,000
Future amortization expense 2022	$ 22,400

Convertible Senior Notes - Narr

Convertible Senior Notes - Narrative (Details) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2014USD ($)d$ / sharesshares	Mar. 31, 2018USD ($)$ / shares	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Debt issued	$ 690,000,000	$ 690,000,000		$ 690,000,000
Threshold trading days exceeding price | d	20
Threshold consecutive trading days exceeding price | d	30
Threshold greater than percentage of stock price trigger	130.00%
Threshold trading days not exceeding price	5 days
Threshold consecutive trading days not exceeding price	5 days
Principal amount per conversion	$ 1,000
Threshold less than percentage of stock price trigger	98.00%
Conversion rate	0.0111651
Conversion price (in dollars per share) | $ / shares	$ 89.56
Potential conversion shares of convertible debt (in shares) | shares	7.7
Fair value of convertible senior notes		$ 712,900,000
Closing price of common stock (in dollars per share) | $ / shares		$ 70.98
Repurchases of common stock	$ 62,000,000	$ 19,785,000	$ 72,467,000
Payments for purchase of convertible note hedge and warrant transactions	23,300,000
Payments for note hedge transactions	$ 101,300,000
Note hedge shares outstanding (in shares) | shares	7.7
Warrants outstanding (in shares) | shares	7.7
Warrant strike price (in dollars per share) | $ / shares	$ 104.49
Proceeds from sale of warrants	$ 78,000,000
Effective interest rate	3.20%

Convertible Senior Notes - Sche

Convertible Senior Notes - Schedule of Convertible Senior Notes (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Feb. 28, 2014
Liability component:
Principal	$ 690,000,000	$ 690,000,000	$ 690,000,000
Less: debt discount and issuance costs, net of amortization	(21,255,000)	(27,087,000)
Net carrying amount	668,745,000	0
Net carrying amount	0	662,913,000
Convertible senior notes
Liability component:
Equity component:	$ 101,276,000	$ 101,276,000

Convertible Senior Notes - Sc48

Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Disclosure [Abstract]
Amortization of debt discount and issuance costs	$ 5,832	$ 5,632
Capitalization of interest expense	(982)	(1,035)
Total interest expense	$ 4,850	$ 4,597

Restructuring (Details)

Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended			15 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 13,100	$ 49,300		$ 62,400
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	14,243
Costs incurred	14,908		$ 0
Cash disbursements	(13,752)
Software and other non-cash charges	(4,605)
Balance as of March 31, 2018	10,794	14,243		10,794
Employee Severance and Related Benefits
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	12,857
Costs incurred	7,163
Cash disbursements	(10,766)
Software and other non-cash charges	0
Balance as of March 31, 2018	9,254	12,857		9,254
Software Charges
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	0
Costs incurred	2,818
Cash disbursements	0
Software and other non-cash charges	(2,818)
Balance as of March 31, 2018	0	0		0
Excess Facilities, Contract Terminations and Other
Restructuring Reserve [Roll Forward]
Balance as of January 1, 2018	1,386
Costs incurred	4,927
Cash disbursements	(2,986)
Software and other non-cash charges	(1,787)
Balance as of March 31, 2018	$ 1,540	$ 1,386		$ 1,540

Commitments and Contingencies -

Commitments and Contingencies - Legal Matters (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Multiple existing lawsuits between Limelight Networks, Inc. (Limelight) and the Company | Settled Litigation
Loss Contingencies [Line Items]
Settlement charge	$ 14.9

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($) shares in Millions	1 Months Ended		3 Months Ended
	Mar. 31, 2018	Feb. 28, 2014	Mar. 31, 2018	Mar. 31, 2017	Feb. 29, 2016
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 1,000,000,000
Repurchase authorization increase	$ 416,700,000
Authorized and available for repurchase	$ 750,000,000		$ 750,000,000
Repurchases of common stock		$ (62,000,000)	(19,785,000)	$ (72,467,000)
Amortization expense from capitalized stock-based compensation			$ 5,600,000	$ 3,500,000
Common Stock [Member]
Class of Stock [Line Items]
Shares repurchased during period (in shares)			0.3

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 44,686	$ 38,986
Provision for income taxes	(11,088)	(17,985)
Total stock-based compensation, net of income taxes	33,598	21,001
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	5,296	4,685
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	10,509	9,029
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	15,959	15,157
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 12,922	$ 10,115

Accumulated Other Comprehensi53

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018	$ 3,362,469
Other comprehensive gain (loss)	3,596	$ 10,737
Balance as of March 31, 2018	3,386,257
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018	(21,930)
Balance as of March 31, 2018	(18,334)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018	(24,319)
Other comprehensive gain (loss)	6,282
Balance as of March 31, 2018	(18,037)
Net Unrealized Gains (Losses) on Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance as of January 1, 2018	2,389
Other comprehensive gain (loss)	(2,686)
Balance as of March 31, 2018	$ (297)

Revenue from Contracts with C54

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)division	Mar. 31, 2017USD ($)
Disaggregation of Revenue [Line Items]
Total revenue	$ 668,724	$ 600,293
Number of divisions | division	2
Web Division
Disaggregation of Revenue [Line Items]
Total revenue	$ 352,837	303,488
Media and Carrier Division
Disaggregation of Revenue [Line Items]
Total revenue	315,887	296,805
U.S.
Disaggregation of Revenue [Line Items]
Total revenue	423,339	398,870
International
Disaggregation of Revenue [Line Items]
Total revenue	$ 245,385	$ 201,423

Revenue from Contracts with C55

Revenue from Contracts with Customers - Performance Obligation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue from Contract with Customer [Abstract]
Revenue recognized	$ 46.4	$ 31
Remaining performance obligation	$ 2,300
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, percentage	70.00%
Remaining performance obligation, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, percentage	30.00%
Remaining performance obligation, expected timing

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	20.70%	28.70%

Net Income per Share - Schedule

Net Income per Share - Schedule of Components Used in Diluted and Basic Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income (in dollars)	$ 53,714	$ 74,583
Denominator:
Shares used for basic net income per share (in shares)	170,116	173,158
Effect of dilutive securities:
Stock options (in shares)	142	360
RSUs and DSUs (in shares)	1,746	1,653
Convertible senior notes (in shares)	0	0
Warrants related to issuance of convertible senior notes (in shares)	0	0
Shares used for diluted net income per share (in shares)	172,004	175,171
Basic net income per share (in dollars per share)	$ 0.32	$ 0.43
Diluted net income per share (in dollars per share)	$ 0.31	$ 0.43

Net Income per Share - Schedu58

Net Income per Share - Schedule of Shares Excluded from Computation of Diluted EPS (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	19,752	19,345
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	0	3
Service-based RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	2,815	2,681
Performance-based RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	1,529	1,253
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	7,704	7,704
Warrants related to issuance of convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	7,704	7,704