Twitter (TWTR) 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 17, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Trading Symbol	TWTR
Entity Registrant Name	TWITTER, INC.
Entity Central Index Key	1418091
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		647,836,523
Entity Public Float			$13,682,971,032

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$1,510,724	$841,010
Short-term investments	2,111,154	1,393,044
Accounts receivable, net of allowance for doubtful accounts of $5,507 and $2,020 as of December 31, 2014 and 2013, respectively	418,454	247,328
Prepaid expenses and other current assets	215,521	93,297
Total current assets	4,255,853	2,574,679
Property and equipment, net	557,019	332,662
Intangible assets	105,011	77,627
Goodwill	622,570	363,477
Other assets	42,629	17,795
Total assets	5,583,082	3,366,240
Current liabilities:
Accounts payable	53,241	27,994
Accrued and other current liabilities	228,233	110,310
Capital leases, short-term	112,320	87,126
Total current liabilities	393,794	225,430
Convertible notes	1,376,020
Capital leases, long-term	118,950	110,520
Deferred and other long-term tax liabilities, net	24,706	59,500
Other long-term liabilities	43,209	20,784
Total liabilities	1,956,679	416,234
Commitments and contingencies (Note 14)
Stockholders' equity:
Preferred stock, $0.000005 par value-- 200,000 shares authorized; none issued and outstanding
Common stock, $0.000005 par value-- 5,000,000 shares authorized; 642,385 and 569,922 shares issued and outstanding as of December 31, 2014 and 2013, respectively	3	3
Additional paid-in capital	5,208,870	3,944,952
Accumulated other comprehensive loss	-10,024	-323
Accumulated deficit	-1,572,446	-994,626
Total stockholders' equity	3,626,403	2,950,006
Total liabilities and stockholders' equity	$5,583,082	$3,366,240

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$5,507	$2,020
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	200,000,000	200,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	5,000,000,000	5,000,000,000
Common stock, shares issued	642,385,000	569,922,000
Common stock, shares outstanding	642,385,000	569,922,000

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenue	$1,403,002	$664,890	$316,933
Costs and expenses
Cost of revenue	446,309	266,718	128,768
Research and development	691,543	593,992	119,004
Sales and marketing	614,110	316,216	86,551
General and administrative	189,906	123,795	59,693
Total costs and expenses	1,941,868	1,300,721	394,016
Loss from operations	-538,866	-635,831	-77,083
Interest income (expense), net	-33,985	-6,860	-2,486
Other income (expense), net	-5,500	-4,455	399
Loss before income taxes	-578,351	-647,146	-79,170
Provision (benefit) for income taxes	-531	-1,823	229
Net loss	($577,820)	($645,323)	($79,399)
Net loss per share attributable to common stockholders:
Basic	($0.96)	($3.41)	($0.68)
Diluted	($0.96)	($3.41)	($0.68)
Weighted-average shares used to compute net loss per share attributable to common stockholders:
Basic	604,990	189,510	117,401
Diluted	604,990	189,510	117,401

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net loss	($577,820)	($645,323)	($79,399)
Other comprehensive income (loss):
Unrealized gain (loss) on investments in available-for-sale securities, net of tax	-877	-76	41
Foreign currency translation adjustment	-8,824	410	-666
Net change in accumulated other comprehensive loss	-9,701	334	-625
Comprehensive loss	($587,521)	($644,989)	($80,024)

CONSOLIDATED_STATEMENTS_OF_RED

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (USD $)	Total	Redeemable Convertible Preferred Stock	Convertible Preferred Stock	Common Stock	Common Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
In Thousands, except Share data	USD ($)	USD ($)	USD ($)	USD ($)	Redeemable Convertible Preferred Stock	Convertible Preferred Stock	USD ($)	USD ($)	USD ($)
						USD ($)
Balance, beginning of period at Dec. 31, 2011		$49	$835,073	$1			$68,097	($32)	($269,904)
Balance, beginning of period, shares at Dec. 31, 2011		135,000	329,575,000	118,967,000
Issuance of stock in connection with acquisitions		37,057					12,399
Issuance of stock in connection with acquisitions, shares		2,742,000		674,000
Issuance of restricted stock to employees in connection with acquisitions, shares		704,000
Forfeiture of restricted stock, shares		-12,000
Series G convertible preferred stock issuance cost adjustment			357
Stock-based compensation for restricted stock issued in connection with acquisitions							3,815
Stock-based compensation for restricted stock issued in connection with acquisitions, shares				903,000
Exercise of stock options							2,317
Exercise of stock options, shares				5,577,000
Other activities, shares				-524,000
Stock-based compensation							14,052
Other activities							1,107
Other comprehensive income (loss)	-625							-625
Net loss	-79,399								-79,399
Balance, end of period at Dec. 31, 2012	-248,172	37,106	835,430	1			101,787	-657	-349,303
Balance, end of period, shares at Dec. 31, 2012	125,597,000	3,569,000	329,575,000	125,597,000
Issuance of stock in connection with acquisitions							335,913
Issuance of stock in connection with acquisitions, shares				17,665,000
Forfeiture of restricted stock, shares		-45,000
Conversion of preferred stock to common stock		-37,106	-835,430			2	872,534
Conversion of preferred stock to common stock, shares		-3,524,000	-329,575,000		3,524,000	329,575,000
Stock-based compensation for restricted stock issued in connection with acquisitions							31,708
Stock-based compensation for restricted stock issued in connection with acquisitions, shares				5,775,000
Exercise of stock options							8,751
Exercise of stock options, shares				7,408,000
Issuance of common stock upon initial public offering							2,019,741
Issuance of common stock upon initial public offering, shares				80,500,000
Other activities, shares				-122,000
Shares withheld related to net share settlement of equity awards							-14,637
Stock-based compensation							564,440
Reclassification of preferred stock liability and preferred stock warrant liability to additional paid-in capital							24,241
Other activities							474
Other comprehensive income (loss)	334							334
Net loss	-645,323								-645,323
Balance, end of period at Dec. 31, 2013	2,950,006			3			3,944,952	-323	-994,626
Balance, end of period, shares at Dec. 31, 2013	569,922,000			569,922,000
Issuance of stock in connection with acquisitions							147,958
Issuance of stock in connection with acquisitions, shares				3,326,000
Issuance of common stock in connection with RSU vesting, shares				42,748,000
Stock-based compensation for restricted stock issued in connection with acquisitions							63,880
Stock-based compensation for restricted stock issued in connection with acquisitions, shares				2,337,000
Exercise of stock options							28,881
Exercise of stock options, shares	22,447,000			22,447,000
Issuance of common stock upon purchases under employee stock purchase plan							42,402
Issuance of common stock upon purchases under employee stock purchase plan, shares	1,900,000			1,887,000
Issuance of common stock upon initial public offering							-240
Shares withheld related to net share settlement of equity awards, shares				-307,000
Other activities, shares				25,000
Shares withheld related to net share settlement of equity awards							-17,053
Stock-based compensation							608,491
Equity component of the convertible note issuance, net	100						505,982
Purchase of convertible note hedge							-407,169
Issuance of warrants							289,272
Other activities							1,514
Other comprehensive income (loss)	-9,701							-9,701
Net loss	-577,820								-577,820
Balance, end of period at Dec. 31, 2014	$3,626,403			$3			$5,208,870	($10,024)	($1,572,446)
Balance, end of period, shares at Dec. 31, 2014	642,385,000			642,385,000

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net loss	($577,820)	($645,323)	($79,399)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	208,165	110,894	72,506
Stock-based compensation expense	631,597	600,367	25,741
Amortization of discount on convertible notes	18,823
Provision for bad debt	4,632	1,557	1,844
Deferred income tax benefit	-9,609	-8,902	-1,098
Non-cash acquisition-related costs	320	704	1,715
Amortization of investment premium and other	7,663	3,457	4,102
Changes in assets and liabilities, net of assets acquired and liabilities assumed from acquisitions:
Accounts receivable	-177,583	-112,060	-73,898
Prepaid expenses and other assets	-165,395	-12,045	-6,691
Accounts payable	18,059	7,957	2,931
Accrued and other liabilities	122,944	54,792	24,312
Net cash provided by (used in) operating activities	81,796	1,398	-27,935
Cash flows from investing activities
Purchases of property and equipment	-201,630	-75,744	-50,599
Purchases of marketable securities	-2,937,033	-1,573,489	-542,638
Proceeds from maturities of marketable securities	2,029,518	355,270	621,049
Proceeds from sales of marketable securities	188,092	42,816	26,300
Restricted cash	-11,042	-10,847	-3,143
Business combinations, net of cash acquired and purchases of intangible assets	-165,177	-44,072	-1,526
Net cash provided by (used in) investing activities	-1,097,272	-1,306,066	49,443
Cash flows from financing activities
Net proceeds from issuance of common stock upon initial public offering		2,018,579
Proceeds from issuance of convertible notes	1,889,000
Convertible notes initial issuance discount	-28,810
Purchases of convertible note hedges	-407,169
Proceeds from issuance of warrants	289,272
Taxes paid related to net share settlement of equity awards	-17,053	-14,637
Repayments of capital lease obligations	-103,135	-70,445	-39,436
Proceeds from exercise of stock options, net of repurchase	28,658	8,679	2,312
Proceeds from issuances of common stock under employee stock purchase plan	42,402
Other financing activities	-1,443
Net cash provided by (used in) financing activities	1,691,722	1,942,176	-37,124
Net increase (decrease) in cash and cash equivalents	676,246	637,508	-15,616
Foreign exchange effect on cash and cash equivalents	-6,532	174	-52
Cash and cash equivalents at beginning of period	841,010	203,328	218,996
Cash and cash equivalents at end of period	1,510,724	841,010	203,328
Supplemental cash flow data
Interest paid in cash	10,000	6,850	3,126
Taxes paid in cash	14,895	2,391	358
Supplemental disclosures of non-cash investing and financing activities
Conversion of preferred stock to common stock		872,536
Common and convertible preferred stock issued in connection with acquisitions	147,958	331,766	47,127
Equipment purchases under capital leases	140,685	155,722	110,206
Changes in accrued equipment purchases	6,562	-1,602	15,734
Unpaid deferred offering costs		$1,162

The_Company

The Company	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
The Company	Note 1. The Company
	Twitter, Inc. (“Twitter” or the “Company”) was incorporated in Delaware in April 2007, and is headquartered in San Francisco, California. Twitter offers products and services for users, advertisers, developers and platform and data partners.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies
	Basis of Presentation
	The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.
	Use of Estimates
	The preparation of the Company’s consolidated financial statements in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, as well as related disclosure of contingent assets and liabilities. Actual results could differ materially from the Company’s estimates. To the extent that there are material differences between these estimates and actual results, the Company’s financial condition or operating results will be affected. The Company bases its estimates on past experience and other assumptions that the Company believes are reasonable under the circumstances, and the Company evaluates these estimates on an ongoing basis.
	Revenue Recognition
	The Company generates revenue principally from the sale of advertising services and, to a lesser extent, from entering into data licensing and other arrangements. The Company’s advertising services include three primary products: (i) Promoted Tweets, (ii) Promoted Accounts and (iii) Promoted Trends. Promoted Tweets and Promoted Accounts are pay-for-performance advertising products priced through an auction. Promoted Trends are featured by geography and offered on a fixed-fee-per-day basis. Advertisers are obligated to pay when a user engages with a Promoted Tweet or follows a Promoted Account or when a Promoted Trend is displayed. Users engage with Promoted Tweets by clicking on a link in a Promoted Tweet, expanding, retweeting, favoriting or replying to a Promoted Tweet or following the account that tweets a Promoted Tweet. These products may be sold in combination as a multiple element arrangement or separately on a stand-alone basis. Fees for these advertising services are recognized in the period when advertising is delivered as evidenced by a user engaging with a Promoted Tweet, as captured by a click, following a Promoted Account or through the display of a Promoted Trend on the Company’s platform. Data licensing revenue is generated based on monthly service fees charged to the data partners over the period in which the Company’s data and data products are made available to them. Other revenue is primarily generated from service fees from transactions completed on the mobile ad exchange. The Company’s mobile ad exchange enables buyers and sellers to purchase and sell advertising inventory and matches buyers and sellers. The Company has determined it is not the principal in the purchase and sale of advertising inventory in transactions between third party buyers and sellers on the exchange. Therefore, the Company reports revenue related to its ad exchange services on a net basis.
	Revenue is recognized only when (1) persuasive evidence of an arrangement exists; (2) the price is fixed or determinable; (3) the service is performed; and (4) collectability of the related fee is reasonably assured. While the majority of the Company’s revenue transactions are based on standard business terms and conditions, the Company also enters into non-standard sales agreements with advertisers and data partners that sometimes involve multiple elements.
	For arrangements involving multiple deliverables, judgment is required to determine the appropriate accounting, including developing an estimate of the stand-alone selling price of each deliverable. When neither vendor-specific objective evidence nor third-party evidence of selling price exists, the Company uses its best estimate of selling price (BESP) to allocate the arrangement consideration on a relative selling price basis to each deliverable. The objective of BESP is to determine the selling price of each deliverable when it is sold to advertisers on a stand-alone basis. In determining BESPs, the Company takes into consideration various factors, including, but not limited to, prices the Company charges for similar offerings, sales volume, geographies, pricing strategies and market conditions. Multiple deliverable arrangements primarily consist of combinations of the Company’s pay-for-performance products, Promoted Tweets and Promoted Accounts, which are priced through an auction, and Promoted Trends, which are priced on a fixed-fee-per day per geography basis. For arrangements that include a combination of these products, the Company develops an estimate of the selling price for these products in order to allocate any potential discount to all advertising products in the arrangement. The estimate of selling price for pay-for-performance products is determined based on the winning bid price; the estimate of selling price for Promoted Trends is based on Promoted Trends sold on a stand-alone basis and/or separately priced in a bundled arrangement by reference to a list price by geography which is approved periodically. The Company believes the use of BESP results in revenue recognition in a manner consistent with the underlying economics of the transaction and allocates the arrangement consideration on a relative selling price basis to each deliverable.
	Cost of Revenue
	Cost of revenue consists primarily of data center costs related to the Company’s co-located facilities, which includes lease and hosting costs, related support and maintenance costs and energy and bandwidth costs, as well as depreciation of its servers and networking equipment, networking costs and personnel-related costs, including salaries, benefits and stock-based compensation, for its operations teams. Cost of revenue also includes allocated facilities and other supporting overhead costs, amortization expense of technology acquired through acquisitions and capitalized labor costs.
	Stock-Based Compensation Expense
	The Company accounts for stock-based compensation expense under the fair value recognition and measurement provisions of U.S. GAAP. Stock-based awards granted to employees are measured based on the grant-date fair value with the resulting expense recognized over the respective period during which the award recipient is required to provide service.
	Pre-2013 RSUs, as defined and further described in Note 12—Common Stock and Stockholders’ Equity (Deficit), vest upon satisfaction of both a service condition and a performance condition. The service condition for these awards is generally satisfied over four years. The performance condition was satisfied in February 2014 pursuant to the terms of the Company’s 2007 Equity Incentive Plan. Prior to the closing of the Company’s initial public offering in November 2013, the Company had not recognized any stock-based compensation expense for the Pre-2013 RSUs, because the performance condition had not been satisfied. As the satisfaction of the performance condition became probable upon completion of the Company’s initial public offering for the Pre-2013 RSUs for which the service condition had been satisfied as of such date, the Company recorded the cumulative stock-based compensation expense for these RSUs during the three months ended December 31, 2013, using the accelerated attribution method. The remaining unrecognized stock-based compensation expense related to the Pre-2013 RSUs will be recorded over the remaining requisite service period using the accelerated attribution method.
	Post-2013 RSUs, as defined and further described in Note 12—Common Stock and Stockholders’ Equity (Deficit), are not subject to a performance condition in order to vest. The service condition for these awards is generally satisfied over four years. The compensation expense related to these RSUs is recognized on a straight-line basis over the requisite service period.
	The Company estimates the fair value of stock options granted and stock purchase rights provided under the Company’s employee stock purchase plan using the Black-Scholes option pricing model on the dates of grant. Calculating the fair value using the Black-Scholes model requires various judgmental assumptions including the expected term and stock price volatility. The Company estimates the expected term of stock options granted based on the simplified method. The Company estimates the expected volatility of its common stock on the dates of grant based on a combination of the Company’s historical stock price volatility and implied volatility in the Company’s traded options when such information is available. When the Company’s historical and implied volatility data are not available for the related awards’ expected term, an average of volatility rates including the historical volatility of a group of comparable, publicly-traded companies is used. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Expected dividend yield is zero percent as the Company has not paid and does not anticipate paying dividends on its common stock. The compensation expense related to stock options and employee stock purchase rights is recognized on a straight-line basis over the requisite service period.
	The Company issues restricted stock subject to a lapsing right of repurchase to continuing employees of certain acquired companies. Since these issuances are subject to post-acquisition employment, the Company accounts for them as post-acquisition stock-based compensation expense. The grant-date fair value of restricted stock granted in connection with acquisitions is recognized as stock-based compensation expense on a straight-line basis over the requisite service period.
	Stock-based compensation expense is recorded net of estimated forfeitures. The Company estimates the forfeiture rate based on historical forfeitures of stock-based awards and adjusts the rate to reflect changes in facts and circumstances, if any.
	Acquisitions
	The Company accounts for acquisitions of entities that include inputs and processes and have the ability to create outputs as business combinations in accordance with Accounting Standards Codification (“ASC”) Topic 805 Business Combinations. The purchase price of the acquisition is allocated to the tangible and intangible assets acquired and liabilities assumed based on their estimated fair values at the acquisition dates. The excess of the purchase price over those fair values is recorded as goodwill. During the measurement period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the consolidated statements of operations.
	Costs to exit or restructure certain activities of an acquired company or the Company’s internal operations are accounted for as one-time termination and exit costs and are accounted for separately from the business combination. Restructuring and other acquisition-related costs are expensed as incurred.
	Operating and Capital Leases
	The Company leases office space and data center facilities under operating leases. Certain lease agreements contain free or escalating rent payment provisions. The Company recognizes rent expense under such leases on a straight-line basis over the term of the lease. Lease renewal periods are considered on a lease-by-lease basis in determining the lease term.
	The Company also enters into server and networking equipment lease arrangements with original lease terms ranging from two to four years. The classification of each lease arrangement is determined in accordance with the criteria outlined in ASC Topic 840 Leases. The Company’s server and networking equipment leases typically are accounted for as capital leases as they meet one or more of the four capital lease classification criteria. Assets acquired under capital leases are amortized over the shorter of the remaining lease term or their estimated useful life. As of December 31, 2014 and 2013, the Company had capital lease obligations included in short-term and long-term capital lease obligations in the consolidated balance sheets of $231.3 million and $197.6 million, respectively. In the years ended December 31, 2014, 2013 and 2012, the Company recorded approximately $10.2 million, $7.0 million and $3.1 million, respectively, of interest expense in relation to these capital lease arrangements.
	Cash, Cash Equivalents and Investments
	The Company invests its excess cash primarily in short-term interest-bearing obligations, including government and investment-grade debt securities and money market funds. The Company classifies all liquid investments with stated maturities of three months or less from date of purchase as cash equivalents.  The Company classifies investments with stated maturities of greater than three months and less than 12 months from the date of purchase as short-term investments and those with stated maturities of 12 months or greater as long-term investments in the consolidated balance sheets. As of December 31, 2014 and 2013, the Company did not hold any long-term investments. As of December 31, 2014 and 2013, the Company has recorded restricted cash balances of $2.6 million and $4.9 million, respectively, within prepaid expenses and other current assets and $28.3 million and $15.3 million, respectively, in other assets on the accompanying consolidated balance sheets based upon the term of the remaining restrictions. These restricted cash balances are primarily related to certain operating lease arrangements.
	The Company determines the appropriate classification of its investments in marketable securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its marketable securities as available-for-sale. After considering the Company’s capital preservation objectives, as well as its liquidity requirements, the Company may sell securities prior to their stated maturities. The Company carries its available-for-sale securities at fair value, and reports the unrealized gains and losses, net of taxes, as a component of stockholders’ equity (deficit), except for unrealized losses determined to be other than temporary which are recorded as other income (expense), net. The Company determines any realized gains or losses on the sale of marketable securities on a specific identification method and records such gains and losses as a component of other income (expense), net. Interest earned on investments in marketable securities was $1.9 million, $0.7 million, and $0.8 million during the years ended December 31, 2014, 2013 and 2012, respectively. These balances are recorded in interest income (expense), net in the accompanying consolidated statements of operations.
	The Company evaluates the investments periodically for possible other-than-temporary impairment. A decline in fair value below the amortized costs of debt securities is considered an other-than-temporary impairment if the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the entire amortized cost basis. In those instances, an impairment charge equal to the difference between the fair value and the amortized cost basis is recognized in earnings. Regardless of the Company’s intent or requirement to sell a debt security, impairment is considered other-than-temporary if the Company does not expect to recover the entire amortized cost basis.
	Concentration of Credit Risk
	Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. The primary focus of the Company’s investment strategy is to preserve capital and meet liquidity requirements. The Company’s investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, the Company invests cash, cash equivalents and short-term investments in a variety of fixed income securities, including short-term interest-bearing obligations, including government and investment-grade debt securities and money market funds. The Company places its cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any.
	The Company’s accounts receivable are typically unsecured and are derived from customers around the world in different industries. The Company performs ongoing credit evaluations of its customers and maintains allowances for potential credit losses. Historically, such losses have been within management’s expectations. As of December 31, 2014 and 2013, no single customer accounted for more than 10% of the Company’s net accounts receivable balance. No single customer accounted for more than 10% of the Company’s revenue in the years ended December 31, 2014, 2013 and 2012.
	The Company’s note hedge transactions, entered into in connection with the Notes, expose the Company to credit risk to the extent that its counterparties may be unable to meet the terms of the transactions. The Company mitigates this risk by limiting its counterparties to major financial institutions.
	Accounts Receivable, Net
	The Company records accounts receivable at the invoiced amount. The Company maintains an allowance for doubtful accounts to reserve for potentially uncollectible receivable amounts. In evaluating the Company’s ability to collect outstanding receivable balances, the Company considers various factors including the age of the balance, the creditworthiness of the customer, which is assessed based on ongoing credit evaluations and payment history, and the customer’s current financial condition.
	Property and Equipment, Net
	Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets. Assets acquired under capital leases and leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful life. The estimated useful lives of property and equipment are described below:
	Property and Equipment	Estimated Useful Life
	Computer hardware and networking equipment	Two to four years
	Computer software	One to three years
	Office equipment and other	Five years
	Leased equipment and leasehold improvements	Lesser of estimated useful life or remaining lease term
	Costs of maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. Upon retirement or sale, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is reflected in operating expenses.
	Goodwill
	Goodwill represents the excess of the purchase price over the fair value of the net tangible and intangible assets acquired in a business combination. Goodwill is not amortized, but is tested for impairment at least annually or more frequently if events or changes in circumstances indicate that the asset may be impaired. The Company’s impairment tests are based on a single operating segment and reporting unit structure. If the carrying value of the reporting unit exceeds its fair value, the second step of the test is performed by comparing the carrying value of the goodwill in the reporting unit to its implied fair value. An impairment charge is recognized for the excess of the carrying value of goodwill over its implied fair value.
	The Company conducted its annual goodwill impairment test during the fourth quarter of 2014 and determined that goodwill was not impaired. As such, no impairment charge was recorded in any of the periods presented in the accompanying consolidated financial statements.
	Intangible Assets
	Intangible assets are carried at cost and amortized on a straight-line basis over their estimated useful lives, which range from one to eleven years. The Company reviews identifiable amortizable intangible assets to be held and used for impairment whenever events or changes in circumstances indicate that the carrying value of the assets may not be recoverable. Determination of recoverability is based on the lowest level of identifiable estimated undiscounted cash flows resulting from use of the asset and its eventual disposition. Measurement of any impairment loss is based on the excess of the carrying value of the asset over its fair value. There has been no impairment charges recorded in any of the periods presented in the accompanying consolidated financial statements. See Note 6—Goodwill and Intangible Assets for additional information.
	Fair Value Measurements
	The Financial Accounting Standards Board (the “FASB”)’s authoritative guidance on fair value measurements establishes a framework for measuring fair value and requires disclosure about the fair value measurements of assets and liabilities. This guidance requires the Company to classify and disclose assets and liabilities measured at fair value on a recurring basis, as well as fair value measurements of assets and liabilities measured on a nonrecurring basis in periods subsequent to initial measurement, in a three-tier fair value hierarchy as described below.
	The guidance defines fair value as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The guidance describes three levels of inputs that may be used to measure fair value:
	Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities.
	Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	Internal Use Software and Website Development Costs
	The Company capitalizes certain costs incurred in developing software programs or websites for internal use. In the years ended December 31, 2014, 2013 and 2012, the Company capitalized costs totaling approximately $79.5 million, $35.6 million and $11.6 million, respectively. The estimated useful life of costs capitalized is evaluated for each specific project and is one to three years. In the years ended December 31, 2014, 2013 and 2012, the amortization of capitalized costs included in cost of revenue totaled approximately $15.2 million, $6.7 million and $5.6 million, respectively. Capitalized internal use software development costs are included in property and equipment, net. Included in the capitalized amounts above are $40.8 million, $13.6 million and $1.3 million of stock-based compensation expense in the years ended December 31, 2014, 2013 and 2012, respectively.
	Income Taxes
	The Company accounts for its income taxes using the asset and liability method whereby deferred tax assets and liabilities are determined based on temporary differences between the bases used for financial reporting and income tax reporting purposes, as well as for operating loss and tax credit carryforwards. Deferred income taxes are provided based on the enacted tax rates expected to be in effect at the time such temporary differences are expected to reverse. A valuation allowance is provided for deferred tax assets if it is more-likely-than-not that the Company will not realize those tax assets through future operations.
	The Company evaluates and accounts for uncertain tax positions using a two-step approach. Recognition (step one) occurs when the Company concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustainable upon examination. Measurement (step two) determines the amount of benefit that is greater than 50% likely to be realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. De-recognition of a tax position that was previously recognized would occur when the Company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained.
	Foreign Currency
	The functional currency of the Company's foreign subsidiaries is generally the local currency. The financial statements of these subsidiaries are translated into U.S. dollars using period-end rates of exchange for assets and liabilities, historical rates of exchange for equity, and average rates of exchange for revenue and expenses. Translation gains (losses) are recorded in accumulated other comprehensive income (loss) as a component of stockholders’ equity. Other income (expense), net in the accompanying consolidated statements of operations consists primarily of unrealized foreign exchange gains and losses due to re-measurement of monetary assets and liabilities denominated in non-functional currencies as well as realized foreign exchange gains and losses on foreign exchange transactions.
	Advertising Costs
	Advertising costs are expensed when incurred and are included in sales and marketing expense in the accompanying consolidated statements of operations. Advertising expense totaled $46.6 million, $3.1 million and $0.7 million for the years ended December 31, 2014, 2013 and 2012 respectively.
	Comprehensive Loss
	Comprehensive loss consists of two components, net loss and other comprehensive income (loss). Other comprehensive income (loss) refers to gains and losses that are recorded as an element of stockholders’ equity and are excluded from net loss. The Company’s other comprehensive income (loss) is comprised of unrealized gains or losses on available-for-sale securities, net of tax, and foreign currency translation adjustment.
Recent Accounting Pronouncements
In May 2014, the FASB issued a new accounting standard update on revenue recognition from contracts with customers. The new guidance will replace all current U.S. GAAP guidance on this topic and eliminate all industry-specific guidance. According to the new guidance, revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration for which the Company expects to be entitled in exchange for those goods or services. This guidance will be effective for the Company beginning January 1, 2017 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is not permitted. The Company has not yet selected a transition method and is evaluating the impact of adopting this new accounting standard update on the financial statements and related disclosures.
In June 2014, the FASB issued a new accounting standard update on stock-based compensation when the terms of an award provide that a performance target could be achieved after the requisite service period. The new guidance requires that a performance target that affects vesting, and that could be achieved after the requisite service period, be treated as a performance condition. As such, the performance target should not be reflected in estimating the grant-date fair value of the award. This update further clarifies that compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the periods for which the requisite service has already been rendered. This guidance will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015 and can be applied either prospectively or retrospectively to all awards outstanding as of the beginning of the earliest annual period presented as an adjustment to opening retained earnings. Early adoption is permitted. Adoption of this new accounting standard update is expected to have no impact to the Company’s financial statements.

Cash_Cash_Equivalents_and_Shor

Cash, Cash Equivalents and Short-term Investments	12 Months Ended
	Dec. 31, 2014
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents and Short-term Investments	Note 3. Cash, Cash Equivalents and Short-term Investments
	Cash, cash equivalents and short-term investments consist of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Cash and cash equivalents:
	Cash	$	147,848	$	164,135
	Money market funds		882,443		229,529
	U.S. government and agency securities including treasury bills		271,418		251,593
	Corporate notes, certificates of deposit and commercial paper		209,015		195,753
	Total cash and cash equivalents	$	1,510,724	$	841,010
	Short-term investments:
	U.S. government and agency securities including treasury bills	$	1,009,541	$	785,536
	Corporate notes, certificates of deposit and commercial paper		1,101,613		607,508
	Total short-term investments	$	2,111,154	$	1,393,044
	The following tables summarize unrealized gains and losses related to available-for-sale securities classified as short-term investments on the Company’s consolidated balance sheets as of December 31, 2014 and 2013 (in thousands):
		31-Dec-14
		Gross			Gross			Gross			Aggregated
		Amortized			Unrealized			Unrealized			Estimated
		Costs			Gains			Losses			Fair Value
	U.S. Government and agency securities including	$	1,009,827		$	8		$	(294	)	$	1,009,541
	treasury bills
	Corporate notes, certificates of deposit and		1,102,275			4			(666	)		1,101,613
	commercial paper
	Total available-for-sale securities classified as	$	2,112,102		$	12		$	(960	)	$	2,111,154
	short-term investments
		31-Dec-13
		Gross			Gross			Gross			Aggregated
		Amortized			Unrealized			Unrealized			Estimated
		Costs			Gains			Losses			Fair Value
	U.S. Government and agency securities including	$	785,535		$	22		$	(21	)	$	785,536
	treasury bills
	Corporate notes, certificates of deposit and		607,590			11			(93	)		607,508
	commercial paper
	Total available-for-sale securities classified as	$	1,393,125		$	33		$	(114	)	$	1,393,044
	short-term investments
	The available-for-sale securities classified as cash and cash equivalents on the consolidated balance sheets are not included in the tables above as the gross unrealized gains and losses were immaterial for each period; their carrying value approximates fair value because of the short maturity period of these instruments.
	The following tables show all short-term investments in an unrealized loss position for which other-than-temporary impairment has not been recognized and the related gross unrealized losses and fair value, aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position (in thousands):
		31-Dec-14
		Less than 12 Months						12 Months or Greater					Total
					Unrealized						Unrealized				Unrealized
		Fair Value			Loss			Fair Value			Loss		Fair Value		Loss
	U.S. Government and agency securities	$	766,997		$	(294	)	$	—		$	—	$	766,997	$	(294	)
	including treasury bills
	Corporate notes, certificates of deposit		525,097			(666	)		—			—		525,097		(666	)
	and commercial paper
	Total short-term investments in an	$	1,292,094		$	(960	)	$	—		$	—	$	1,292,094	$	(960	)
	unrealized loss position
		31-Dec-13
		Less than 12 Months						12 Months or Greater					Total
					Unrealized						Unrealized				Unrealized
		Fair Value			Loss			Fair Value			Loss		Fair Value		Loss
	U.S. Government and agency securities	$	230,478		$	(21	)	$	—		$	—	$	230,478	$	(21	)
	including treasury bills
	Corporate notes, certificates of deposit		171,894			(93	)		—			—		171,894		(93	)
	and commercial paper
	Total short-term investments in an	$	402,372		$	(114	)	$	—		$	—	$	402,372	$	(114	)
	unrealized loss position
	Investments are reviewed periodically to identify possible other-than-temporary impairments. No impairment loss has been recorded on the securities included in the tables above as the Company believes that the decrease in fair value of these securities is temporary and expects to recover up to (or beyond) the initial cost of investment for these securities.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 4. Fair Value Measurements
	The Company measures its cash equivalents and short-term investments at fair value. The Company classifies its cash equivalents and short-term investments within Level 1 or Level 2 because the Company values these investments using quoted market prices or alternative pricing sources and models utilizing market observable inputs. The fair value of the Company’s Level 1 financial assets is based on quoted market prices of the identical underlying security. The fair value of the Company’s Level 2 financial assets is based on inputs that are directly or indirectly observable in the market, including the readily-available pricing sources for the identical underlying security that may not be actively traded.
	The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2014 and 2013 based on the three-tier fair value hierarchy (in thousands):
		31-Dec-14
		Level 1		Level 2		Level 3		Total
	Assets
	Cash equivalents:
	Money market funds	$	882,443	$	—	$	—	$	882,443
	Treasury bills		73,525		—		—		73,525
	U.S. government securities		—		157,895		—		157,895
	Agency securities		—		39,998		—		39,998
	Corporate notes		—		13,684		—		13,684
	Commercial paper		—		185,321		—		185,321
	Certificates of deposit		—		10,010		—		10,010
	Short-term investments:
	Treasury bills		167,575		—		—		167,575
	U.S. government securities		—		746,128		—		746,128
	Agency securities		—		95,838		—		95,838
	Corporate notes		—		551,604		—		551,604
	Commercial paper		—		300,589		—		300,589
	Certificates of deposit		—		249,420		—		249,420
	Total	$	1,123,543	$	2,350,487	$	—	$	3,474,030
		31-Dec-13
		Level 1		Level 2		Level 3		Total
	Assets
	Cash equivalents:
	Money market funds	$	229,529	$	—	$	—	$	229,529
	Treasury bills		244,048		—		—		244,048
	U.S. government securities		—		7,545		—		7,545
	Corporate notes		—		1,011		—		1,011
	Commercial paper		—		194,742		—		194,742
	Short-term investments:
	Treasury bills		265,878		—		—		265,878
	U.S. government securities		—		501,372		—		501,372
	Agency securities		—		18,286		—		18,286
	Corporate notes		—		255,546		—		255,546
	Commercial paper		—		272,617		—		272,617
	Certificates of deposit		—		79,345		—		79,345
	Total	$	739,455	$	1,330,464	$	—	$	2,069,919
	The estimated fair value of the 2019 Notes and 2021 Notes based on a market approach as of December 31, 2014 was approximately $817.5 million and $832.3 million respectively, which represents a Level 2 valuation.  The estimated fair value was determined based on the quoted closing price of the Notes in an over-the-counter market on December 31, 2014.

Property_and_Equipment_Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2014
Property Plant And Equipment [Abstract]
Property and Equipment, Net	Note 5. Property and Equipment, Net
	The following table presents the detail of property and equipment, net for the periods presented (in thousands):
		December 31,			December 31,
		2014			2013
	Property and equipment, net
	Equipment	$	584,561		$	367,949
	Furniture and leasehold improvements		131,851			54,965
	Capitalized software		82,052			47,290
	Construction in progress		89,806			29,523
	Total		888,270			499,727
	Less: Accumulated depreciation and amortization		(331,251	)		(167,065	)
	Property and equipment, net	$	557,019		$	332,662
	The gross carrying amount of property and equipment includes $411.3 million and $283.8 million of server and networking equipment acquired under capital leases as of December 31, 2014 and 2013, respectively. The accumulated depreciation of the equipment under capital leases totaled $182.4 million and $86.2 million as of December 31, 2014 and 2013, respectively.
	Depreciation expense totaled $171.6 million, $94.4 million and $53.8 million for the years ended December 31, 2014, 2013 and 2012, respectively. Included in these amounts were depreciation expense for server and networking equipment acquired under capital leases in the amount of $108.7 million, $70.4 million and $40.5 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Note 6. Goodwill and Intangible Assets
	The following table presents the goodwill activities for the periods presented (in thousands):
	Goodwill
	Balance as of December 31, 2012	$	68,813
	Crashlytics acquisition		33,254
	Bluefin acquisition		60,019
	MoPub acquisition		192,446
	Other acquisitions		8,945
	Balance as of December 31, 2013	$	363,477
	Gnip acquisition		104,747
	Other acquisitions		155,054
	Foreign currency translation adjustment		(708	)
	Balance as of December 31, 2014	$	622,570
	For each of the periods presented, gross goodwill balance equaled the net balance since no impairment charges have been recorded. Refer to Note 8—Acquisitions for further details about goodwill.
	The following table presents the detail of intangible assets for the periods presented (in thousands):
		Gross Carrying			Accumulated			Net Carrying
		Value			Amortization			Value
	December 31, 2014:
	Patents and developed technologies	$	105,052		$	(23,165	)	$	81,887
	Publisher and advertiser relationships		32,000			(9,831	)		22,169
	Assembled workforce		1,960			(1,457	)		503
	Other intangible assets		1,100			(648	)		452
	Total	$	140,112		$	(35,101	)	$	105,011
	December 31, 2013:
	Patents and developed technologies	$	100,553		$	(45,440	)	$	55,113
	Publisher and advertiser relationships		21,100			(1,248	)		19,852
	Assembled workforce		1,960			(300	)		1,660
	Other intangible assets		1,100			(98	)		1,002
	Total	$	124,713		$	(47,086	)	$	77,627
	Patents and developed technologies are amortized over a period ranging from one to eleven years from the respective purchase dates. Publisher and advertiser relationships are amortized over a period ranging from two to three years, and assembled workforce and other intangible assets are amortized over a period of two to four years. Amortization expense associated with intangible assets for the years ended December 31, 2014 and 2013 was $36.6 million and $16.5 million, respectively. During the year ended December 31, 2014, $48.5 million in gross carrying value and accumulated amortization related to fully amortized intangible assets was eliminated.
	Estimated future amortization expense as of December 31, 2014 is as follows (in thousands):
	Years ending December 31,
	2015	$	35,446
	2016		26,260
	2017		11,624
	2018		9,832
	2019		5,430
	Thereafter		16,419
	Total	$	105,011

Other_Balance_Sheet_Components

Other Balance Sheet Components	12 Months Ended
	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Other Balance Sheet Components	Note 7. Other Balance Sheet Components
	Prepaid expenses and other current assets
	The following table presents the detail of prepaid and other current assets for the periods presented (in thousands):
		December 31,		December 31,
		2014		2013
	Deferred income tax assets, net	$	25,882	$	62,122
	Prepaid and other		189,639		31,175
	Total	$	215,521	$	93,297
	Accrued and other current liabilities
	The following table presents the detail of accrued and other current liabilities for the periods presented (in thousands):
		December 31,		December 31,
		2014		2013
	Accrued compensation	$	68,000	$	29,882
	Accrued publisher payments		27,996		15,370
	Accrued sales and marketing expenses		25,264		1,813
	Deferred revenue		18,679		14,479
	Accrued tax liabilities		18,380		9,515
	Accrued professional services		13,543		7,089
	Accrued other		56,371		32,162
	Total	$	228,233	$	110,310

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions	Note 8. Acquisitions
	2014 Acquisitions In May 2014, the Company completed its acquisition of privately held Gnip, Inc. (“Gnip”), a leading provider of social data and analytics headquartered in Boulder, Colorado. The acquisition is expected to allow the Company to further enhance its data analytics capabilities. Under the terms of the acquisition, the Company agreed to pay $107.3 million in cash and issue a total of 0.6 million shares of its common stock, including shares of restricted stock subject to continued employment, in consideration for all of the issued and outstanding shares of capital stock of Gnip. In addition, the Company agreed to issue up to 0.4 million shares of the Company’s common stock as a result of assumed Gnip equity awards held by individuals, who will continue to provide services to the Company. The fair value of the total consideration of $134.1 million, including the earned portion of assumed stock options and other equity awards, was allocated to the acquired tangible and intangible assets and assumed liabilities based on their estimated fair values at closing as follows: $23.2 million to developed technology, $9.3 million to customer relationships, $9.1 million to tangible assets acquired, $5.8 million to liabilities assumed, $6.4 million to deferred tax liability recorded, and the excess $104.7 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. This goodwill is primarily attributable to the potential expansion and future development of the Company’s data products, expected synergies arising from the acquisition and the value of acquired talent. Goodwill is not deductible for U.S. income tax purposes. Both developed technology and customer relationships will be amortized on a straight-line basis over their estimated useful life of 60 months. The discounted cash flow method, which calculates the fair value of an asset based on the value of cash flows that the asset is expected to generate in the future, was used to estimate the fair value of these intangible assets acquired.
	During the year ended December 31, 2014, the Company acquired eight other companies, which were accounted for as business combinations. The total purchase price of $188.1 million (paid in shares of the Company’s common stock having a total fair value of $121.2 million and cash of $66.9 million) for these acquisitions was preliminarily allocated as follows: $28.1 million to developed technologies, $1.6 million to customer relationships, $6.5 million to net tangible assets acquired based on their estimated fair value on the acquisition date, $3.2 million to deferred tax liability, and the excess $155.1 million of the purchase price over the fair value of net assets acquired to goodwill. Tax deductible goodwill resulting from certain of these acquisitions was $21.9 million as of December 31, 2014, the remaining amounts are not tax deductible for U.S. income tax purposes. Developed technologies and customer relationships will be amortized on a straight-line basis over their estimated useful lives of 12 to 48 months.
	In connection with all of the acquisitions completed during the year ended December 31, 2014, the Company also agreed to pay cash and shares of the Company’s common stock with a total fair value up to $97.7 million, which is to be paid to certain employees of the acquired entities contingent upon their continued employment with the Company. In addition, the fair value of assumed stock options determined to be part of post-acquisition stock-based compensation amounted to approximately $16.9 million. The Company recognizes compensation expense in relation to these cash and equity consideration and assumed stock options over the remaining requisite service periods of up to 48 months from the respective acquisition dates on a straight-line basis.
	The results of operations for each of these acquisitions have been included in the Company’s consolidated statements of operations since the date of acquisition. Actual and pro forma revenue and results of operations for these acquisitions have not been presented because they do not have a material impact to the consolidated revenue and results of operations, either individually or in aggregate.
	2013 Acquisitions
	In January 2013, the Company acquired Crashlytics, Inc. (“Crashlytics”), a privately-held company based in Cambridge, Massachusetts, which developed mobile application crash reporting and analysis solutions for mobile application developers. The acquisition of Crashlytics has been accounted for as a business combination. The purchase price of $38.2 million paid in the Company’s common stock was allocated as follows: $5.0 million to developed technology, $0.3 million to assets acquired, $0.3 million to deferred tax liability recorded and $0.1 million to liabilities assumed, and the excess $33.3 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. Goodwill is primarily attributable to the Company’s ability to further improve the efficiency and the overall performance of its mobile platform and the value of acquired talent. This goodwill is not deductible for U.S. income tax purposes. Developed technology will be amortized on a straight-line basis over its estimated useful life of 12 months. Under the terms of the acquisition, the Company has the right to the return of shares issued to non-employee investors if specified performance conditions tied to certain key employees’ continued employment at the Company for one year after the acquisition are not met. The fair value of these contingently returnable shares of $6.7 million is included in the purchase price and is classified as part of stockholders’ equity (deficit) on the consolidated balance sheets. As of December 31, 2014, the performance condition has been fully satisfied for these shares.
	In February 2013, the Company acquired Bluefin Labs, Inc. (“Bluefin”), a privately-held company based in Cambridge, Massachusetts, which provided social television analytics services to brand advertisers, agencies and TV networks. The acquisition of Bluefin has been accounted for as a business combination. The purchase price of $67.3 million paid in the Company’s common stock was allocated as follows: $7.4 million to developed technology, $1.8 million to assets acquired and $1.9 million to liabilities assumed based on their estimated fair value on the acquisition date, and the excess $60.0 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. This goodwill is primarily attributable to the potential for future product offering, ability to further enhance the advertiser experience in using the Company’s services and the value of acquired talent. Goodwill is not deductible for U.S. income tax purposes. Developed technology will be amortized on a straight-line basis over its estimated useful life of 18 months. Under the terms of the acquisition, the Company has the right to the return of shares issued to non-employee investors if specified performance conditions tied to certain key employees’ continued employment at the Company for one year after the acquisition are not met. The fair value of these contingently returnable shares of $7.9 million is included in the purchase price and is classified as part of stockholders’ equity (deficit) on the consolidated balance sheets. As of December 31, 2014, the performance condition has been fully satisfied for these shares.
	In October 2013, the Company acquired 100% of the ownership interest in privately held MoPub, Inc. (“MoPub”), a mobile-focused advertising exchange headquartered in San Francisco, California. Under the terms of the acquisition, all of the issued and outstanding shares of capital stock of MoPub, including shares of restricted stock subject to continued employment, were converted into 11.2 million shares of the Company’s common stock and 2.0 million shares of unvested restricted stock, and all equity awards to purchase shares of MoPub common stock held by individuals, who will continue to provide services to the Company, were converted into the right to receive an aggregate of 1.2 million shares of the Company’s stock options.  Of the aggregate acquisition consideration, approximately $218.8 million associated with the common stock issued and the fair value attributable to the portion of restricted stock and assumed stock options for which services had been rendered as of the closing of the acquisition was determined to be the accounting purchase price.  The purchase price was allocated to the acquired tangible and intangible assets and assumed liabilities based on their estimated fair values at closing as follows: $21.1 million to publisher and advertiser relationships, $12.9 million to developed technology, $1.1 million to trade name, $22.1 million to account receivables acquired, which are expected to be substantially collected, $1.2 million to other tangible assets acquired, $22.1 million to publisher payments liabilities assumed, $4.4 million to other liabilities assumed, $5.5 million to deferred tax liability recorded, and the excess $192.4 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. This goodwill is primarily attributable to the potential expansion of the advertising business across the mobile ecosystem through continued investment in the MoPub exchange and expected synergies arising from the acquisition, the ability to further enhance the advertiser experience by building real-time bidding into the Twitter ads platform and the value of acquired talent. Goodwill is not deductible for U.S. income tax purposes. Publisher and advertiser relationships and developed technology will be amortized on a straight-line basis over their estimated useful life of 36 months, and trade name will be amortized on a straight-line basis over its estimated useful life of 24 months.
	During the year ended December 31, 2013, the Company completed acquisitions of certain intangible assets for the total purchase price of $38.5 million. These transactions were accounted for as a purchase of assets and, accordingly, the total purchase price was allocated to the identifiable intangible assets acquired based on their respective fair values on the acquisition date. As a result of these transactions, the Company recorded intangible assets of $38.5 million, which was comprised of $36.0 million of patents, $2.0 million of assembled workforce and $0.5 million of developed technology. The patents, developed technology and assembled workforce will be amortized on a straight-line basis over their estimated useful lives of 1 to 11 years.
	During the year ended December 31, 2013, the Company completed acquisitions of five additional companies, which were not individually significant and accounted for as business combinations. The total purchase price for these acquisitions of $13.2 million (paid in shares of the Company’s common stock valued at approximately $7.4 million and cash consideration of $5.8 million) was primarily allocated to $4.5 million of developed technology and $0.2 million of assumed liabilities based on their estimated fair value on the acquisition date, and the excess $8.9 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. Goodwill recorded in relation to these acquisitions is primarily attributable to expected synergies and the value of acquired assembled workforce. Two of the acquisitions resulted in tax-deductible goodwill of $7.3 million for U.S. income tax purposes. Developed technology will be amortized on a straight-line basis over their estimated useful lives of 24 to 36 months.
	In relation to the 2013 acquisitions, the Company also agreed to pay up to $83.1 million of equity consideration which was to be paid to certain employees of the acquired entities contingent upon their continued employment with the Company. The Company recognizes compensation expense related to the equity consideration over the requisite services periods of up to 48 months from the respective acquisition dates on a straight-line basis. The Company also granted to continuing employees options to purchase a total of 2.0 million shares of common stock in exchange for their outstanding options to purchase the shares of the acquired entities including 1.2 million shares granted in connection with the acquisition of MoPub disclosed above. Excluding the fair value of the stock options that was allocated and recorded as part of the purchase price for the portion of the service period completed pre-acquisition, the Company will recognize approximately $24.5 million of stock-based compensation expense in relation to these stock options over the remaining requisite service periods of up to 48 months from the respective acquisition dates on a straight-line basis.
	For business combinations closed in 2013 except for the acquisition of MoPub, the Company has considered all potential identifiable intangible assets and determined that it was not appropriate to allocate material amounts to identifiable intangible assets other than acquired developed technologies. In valuing these acquired developed technologies, the Company determined that neither the income approach nor the market approach was relevant, and, consistent with a market participant approach that would weigh a “make” versus “buy” decision when considering the acquisition of a particular incremental technology, applied the cost approach in determining the amount of purchase price allocated to acquired developed technology. The cost approach uses the concept of reproduction cost as an indicator of fair value. The premise of the cost approach is that a prudent investor would pay no more for an asset than the amount for which the asset could be replaced with a new one. Reproduction cost refers to the cost incurred to reproduce the asset using the exact same specifications. In order to apply the cost method to determine the fair value of each acquired developed technology, the Company considered the following: (i) the estimated development hours or equivalent of person months required to reproduce the technology, (ii) the related labor cost and (iii) an expected market participant profit margin.
	The Company utilized various forms of the income approach to measure the fair value of the publisher relationships, advertiser relationships, developed technology, and trade name acquired in the acquisition of MoPub. For the publisher relationships, fair value was determined based on the multi-period excess earnings approach which calculates the present value of the after-tax cash flows attributable to the intangible asset only. For the advertiser relationships, fair value was determined based on the distributor method which relies upon market-based distributor data to reasonably isolate the revenue, earnings, and cash flow attributable to sales efforts. For the developed technology and trade names acquired, fair value was determined based on the relief from royalty method, which calculates the present value of the after-tax royalty savings attributable to owning the intangible assets.
	For certain transactions that were considered asset acquisitions, the Company identified assembled workforce as an intangible asset. The Company used the cost approach to value the assembled workforce. The cost approach takes into consideration the relevant costs to replace the workforce, which include recruiting and training costs required until the employees become fully integrated.
	The results of operations for each of these acquisitions have been included in the Company’s consolidated statements of operations since the date of acquisition. Revenue and loss from operations arising from the acquisitions completed in 2013 that are included in the Company’s consolidated statements of operations for 2013 were $9.6 million and $42.3 million, respectively.
	The following summary of unaudited pro forma results of operations of the Company for the years ended December 31, 2013 and 2012 is presented using the assumption that the business combinations made in 2013 were completed as of January 1, 2012. These pro forma results of the Company have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which would have resulted had the acquisitions occurred as of January 1, 2012, nor is it indicative of future operating results. The pro forma results presented include amortization charges for acquired intangible assets, adjustments for incremental compensation expense related to the post-combination service arrangements entered into with the continuing employees and related tax effects (in thousands):
		Year Ended December 31,
		2013			2012
		(Unaudited)
	Revenue	$	678,838		$	321,639
	Net loss		(667,404	)		(166,026	)
	2012 Acquisitions
	In January 2012, the Company acquired 100% of the equity interest of Dasient, Inc. (“Dasient”), a privately-held company based in Sunnyvale, California which provided Internet security services to protect advertising networks from malicious ads. The acquisition of Dasient has been accounted for as a business combination. The purchase price of $19.1 million ($0.1 million in cash and $19.0 million in the Company’s Class A junior preferred stock) was allocated as follows: $7.7 million to developed technology, $0.8 million to assets acquired and $1.4 million to liabilities assumed based on their estimated fair value on the acquisition date, and the excess $12.0 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. This goodwill is primarily attributable to the Company’s ability to further enhance the security of its web platform from malware and other online abuses, its ability to more effectively identify and monitor fraudulent accounts or activities on its platform and the value of acquired talent. Goodwill is not deductible for U.S. income tax purposes. Developed technology was amortized on a straight-line basis over its estimated useful life of 12 months.
	In 2012, the Company acquired nine additional companies. These acquisitions, which were not individually significant, were accounted for as business combinations. The total purchase price for these acquisitions of $33.1 million (paid with the Company’s common stock and Class A junior preferred stock valued at approximately $28.1 million and cash consideration of $5.0 million) was primarily allocated as follows: $8.3 million to developed technology and $4.7 million, of which $3.5 million is cash acquired, to net assets acquired based on their estimated fair value on the acquisition date, and the excess $20.1 million of the purchase price over the fair value of net assets acquired was recorded as goodwill. Goodwill recorded in relation to these acquisitions is primarily attributable to expected synergies and the value of acquired assembled workforce. Five of the acquisitions resulted in tax-deductible goodwill of $10.0 million for U.S. income tax purposes. Developed technology was amortized on a straight-line basis over their estimated useful life of 12 months.
	Under the terms of the acquisitions, the Company has the right to the return of a fixed number of shares issued to non-employee investors if specified performance conditions tied to certain key employees’ continued employment at the Company for one year after the acquisition are not met. The fair value of these contingently returnable shares of approximately $4.0 million and $3.0 million for Class A junior preferred stock and common stock issued, respectively, was included in the purchase price and classified as part of redeemable convertible preferred stock and stockholders’ equity (deficit), respectively, on the consolidated balance sheets. The Company believes that the performance condition will be fully satisfied for these shares. As of December 31, 2014, none of the consideration has been returned to the Company.
	In relation to the 2012 acquisitions, the Company also agreed to pay up to $28.5 million of cash and equity consideration contingent upon the continued employment with the Company of certain employees of the acquired entities. The Company recognizes compensation expense related to these consideration over the requisite service periods of up to 48 months from the respective acquisition dates on a straight-line basis.
	The results of operations for each of these acquisitions have been included in the Company’s consolidated statements of operations since the date of acquisition. Revenue and loss from operations arising from the acquisitions completed in 2012 that are included in the Company’s consolidated statements of operations for 2012 were zero and $26.9 million, respectively.
	The following summary of unaudited pro forma results of operations of the Company for the years ended December 31, 2012 and 2011 is presented using the assumption that the acquisitions made in 2012 were completed as of January 1, 2011. These pro forma results of the Company have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which would have resulted had the acquisitions occurred as of January 1, 2011, nor is it indicative of future operating results. The pro forma results presented include amortization charges for acquired intangible assets, adjustments for incremental compensation expense related to the post-combination service arrangements entered into with the continuing employees and related tax effects (in thousands):
		Year Ended December 31,
		2012			2011
		(Unaudited)
	Revenue	$	316,933		$	106,313
	Net loss		(70,200	)		(166,317	)

Convertible_Notes

Convertible Notes	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Convertible Notes	Note 9. Convertible Notes
	In September 2014, the Company issued $900.0 million principal amount of 2019 Notes and $900.0 million principal amount of 2021 Notes in a private placement to qualified institutional buyers pursuant to Rule144A under the Securities Act of 1933, as amended. In October 2014, pursuant to the exercise of the overallotment option by the initial purchasers, the Company issued an additional $35.0 million principal amount of 2019 Notes and $54.0 million principal amount of 2021 Notes. The total net proceeds from this offering were approximately $1.86 billion, after deducting $28.3 million of initial purchasers’ discount and $0.5 million debt issuance costs in connection with the 2019 Notes and the 2021 Notes.
	The interest rates are fixed at 0.25% and 1.00% per annum and are payable semi-annually in arrears on March 15 and September 15 of each year, commencing on March 15, 2015.  During the year ended December 31, 2014, the Company recognized $1.4 million of interest expense related to the amortization of initial purchasers’ discount and debt issuance costs, and $3.3 million of accrued coupon interest expense. These interest expenses are recorded in interest income (expense), net in the consolidated statements of operations.
	Each $1,000 of principal of these notes will initially be convertible into 12.8793 shares of the Company’s common stock, which is equivalent to an initial conversion price of approximately $77.64 per share, subject to adjustment upon the occurrence of specified events.  Holders of these notes may convert their notes at their option at any time until close of business on the second scheduled trading day immediately preceding the relevant maturity date which is March 15, 2019 for the 2019 Notes and March 15, 2021 for the 2021 Notes.  Further, holders of each of these notes may convert their notes at their option prior to the respective dates above, only under the following circumstances:
	1)	during any calendar quarter commencing after the calendar quarter ending on December 31, 2014 (and only during such calendar quarter), if the last reported sale price of Twitter’s common stock for at least 20 trading days (whether or not consecutive) during a 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 for the relevant series of notes on each applicable trading day;
	2)	during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $1,000 principal amount of 2019 notes or 2021 notes, as applicable, for each trading day of the measurement period was less than 98% of the product of the last reported sale price of Twitter’s common stock and the conversion rate for the notes of the relevant series on each such trading day; or
	3)	upon the occurrence of certain specified corporate events.
	Upon conversion of the 2019 Notes and 2021 Notes, the Company will pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at the Company’s election. If the Company satisfies its conversion obligation solely in cash or through payment and delivery, as the case may be, of a combination of cash and shares of its common stock, the amount of cash and shares of common stock, if any, due upon conversion will be based on a daily conversion value (as described herein) calculated on a proportionate basis for each trading day in a 30 trading day observation period.
	If a fundamental change (as defined in the relevant indenture governing the applicable series of Notes) occurs prior to the maturity date, holders of the 2019 Notes and 2021 Notes may require the Company to repurchase all or a portion of their notes for cash at a repurchase price equal to 100% of the principal amount of the notes, plus any accrued and unpaid interest to, but excluding, the repurchase date. In addition, if specific corporate events occur prior to the applicable maturity date, the Company will be required to increase the conversion rate for holders who elect to convert their notes in certain circumstances.
	In accordance with accounting guidance on embedded conversion features, the Company valued and bifurcated the conversion option associated with the 2019 Notes and 2021 Notes from the respective host debt instrument, which is referred to as debt discount, and initially recorded the conversion option of $222.8 million for the 2019 Notes and $283.3 million for the 2021 Notes in stockholders’ equity. The resulting debt discounts on the 2019 Notes and 2021 Notes are being amortized to interest expense at an effective interest rate of 5.75% and 6.25%, respectively, over the contractual terms of the notes. The Company allocated $0.1 million of debt issuance costs to the equity component, and the remaining debt issuance costs of $0.4 million are being amortized to interest expense.
	During the year ended December 31, 2014, the Company recognized $18.8 million of interest expense related to the amortization of the debt discount. This interest expense is recorded in interest income (expense), net in the consolidated statements of operations. As of December 31, 2014, the net carrying value, net of the initial purchasers’ discount and debt discount, of 2019 Notes and 2021 Notes was $709.9 million and $666.1 million, respectively.
	The Notes consisted of the following (in thousands):
			31-Dec-14
			2019 Notes			2021 Notes
	Principal amounts:
	Principal		$	935,000		$	954,000
	Unamortized initial purchasers' discount and debt discount (1)			(225,104	)		(287,876	)
	Net carrying amount		$	709,896		$	666,124
	Carrying amount of the equity component (2)		$	222,826		$	283,283
	-1	Included in the consolidated balance sheets within convertible notes and amortized over the remaining lives of the Notes.
	-2	Included in the consolidated balance sheets within additional paid-in capital.
	As of December 31, 2014, the remaining life of the 2019 Notes and 2021 Notes is approximately 56 months and 80 months, respectively.
	Concurrently with the offering of these notes in September and October 2014, the Company entered into convertible note hedge transactions with certain bank counterparties whereby the Company has the option to purchase initially (subject to adjustment for certain specified events) a total of approximately 24.3 million shares of its common stock at a price of approximately $77.64 per share. The total cost of the convertible note hedge transactions was $407.2 million. In addition, the Company sold warrants to certain bank counterparties whereby the holders of the warrants have the option to purchase initially (subject to adjustment for certain specified events) a total of approximately 24.3 million shares of the Company’s common stock at a price of $105.28. The Company received $289.3 million in cash proceeds from the sale of these warrants.
	Taken together, the purchase of the convertible note hedges and the sale of warrants are intended to offset any actual dilution from the conversion of these notes and to effectively increase the overall conversion price from $77.64 to $105.28 per share. As these transactions meet certain accounting criteria, the convertible note hedges and warrants are recorded in stockholders’ equity and are not accounted for as derivatives. The net cost incurred in connection with the convertible note hedge and warrant transactions was recorded as a reduction to additional paid-in capital in the consolidated balance sheet as of December 31, 2014.

Net_Loss_Per_Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Loss Per Share	Note 10. Net Loss per Share
	The Company computes net loss per share of common stock in conformity with the two-class method required for participating securities. The Company considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities, because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. Prior to their conversion to common stock, the Company also considered all series of the Company’s redeemable convertible preferred stock and convertible preferred stock to be participating securities as the holders of the preferred stock were entitled to receive a noncumulative dividend on a pari passu basis in the event that a dividend was paid on common stock. The holders of all series of convertible preferred stock and the holders of early exercised shares subject to repurchase do not have a contractual obligation to share in the losses of the Company. As such, the Company’s net losses for the years ended December 31, 2014, 2013 and 2012 were not allocated to these participating securities.
	Basic net loss per share is computed by dividing total net loss attributable to common stockholders by the weighted-average common shares outstanding. The weighted-average common shares outstanding is adjusted for shares subject to repurchase such as unvested restricted stock granted to employees in connection with acquisitions, contingently returnable shares and escrowed shares supporting indemnification obligations that are issued in connection with acquisitions and unvested stock options exercised. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding including potential dilutive common stock instruments. In the years ended December 31, 2014, 2013 and 2012, the Company’s potential common stock instruments such as stock options, RSUs, shares to be purchased under the Employee Stock Purchase Plan, shares subject to repurchases and the warrants were not included in the computation of diluted loss per share as the effect of including these shares in the calculation would have been anti-dilutive.
	The following table presents the calculation of basic and diluted net loss per share for periods presented (in thousands, except per share data).
		Year Ended December 31,
		2014				2013				2012
	Net loss	$	(577,820	)		$	(645,323	)		$	(79,399	)
	Basic shares:
	Weighted-average common shares outstanding		613,944				196,675				120,845
	Weighted-average restricted stock		(8,954	)			(7,165	)			(3,444	)
	subject to repurchase
	Weighted-average shares used to compute		604,990				189,510				117,401
	basic net loss per share
	Diluted shares:
	Weighted-average shares used to compute		604,990				189,510				117,401
	diluted net loss per share
	Net loss per share attributable to common stockholders:
	Basic	$	(0.96	)		$	(3.41	)		$	(0.68	)
	Diluted	$	(0.96	)		$	(3.41	)		$	(0.68	)
	The following number of potential common shares at the end of each period were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive for the periods presented (in thousands):
		Year Ended December 31,
		2014			2013				2012
	RSUs		64,135				95,723				42,526
	Warrants		24,329				117				117
	Stock options		20,420				42,246				48,787
	Shares subject to repurchase		8,051				10,986				4,237
	Employee stock purchase plan		1,284				1,896				—
	Since the Company expects to settle the principal amount of the outstanding Notes in cash, the Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable.  The conversion spread of 24.3 million shares will have a dilutive impact on diluted net income per share of common stock when the average market price of the Company’s common stock for a given period exceeds the conversion price of $77.64 per share for the Notes.
	If the average market price of the common stock exceeds the exercise price of the warrants, $105.28, the warrants will have a dilutive effect on the earnings per share assuming that the Company is profitable.  Since the average market price of the common stock is below $105.28, the warrants are anti-dilutive.

Preferred_Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2014
Temporary Equity Disclosure [Abstract]
Preferred Stock
	Note 11. Preferred Stock
	Prior to the initial public offering, the Company had outstanding 3.5 million shares of Class A junior preferred stock.  Immediately prior to the closing of the Company’s initial public offering on November 13, 2013, all shares of outstanding redeemable convertible preferred stock were automatically converted to 3.5 million shares of the Company’s common stock.
	Prior to the initial public offering, the Company also had outstanding 77.0 million shares designated as Series A convertible preferred stock, 49.3 million shares designated as Series B convertible preferred stock, 62.8 million shares designated as Series C convertible preferred stock, 51.0 million shares designated as Series D convertible preferred stock, 38.4 million shares designated as Series E convertible preferred stock, 26.2 million shares designated as Series F convertible preferred stock and 24.9 million shares designated as Series G convertible preferred stock.  Each share of preferred stock was convertible to one share of common stock.  Upon the closing of the Company’s initial public offering on November 13, 2013, all shares of outstanding redeemable convertible preferred stock were automatically converted to 329.6 million shares of the Company’s common stock.
	The Company has the authority to issue up to 200,000,000 shares of preferred stock and to determine the price, rights, preferences, privileges and restrictions, including voting rights, of those shares without any further vote or action by the stockholders. As of December 31, 2014 and 2013, there was no preferred stock outstanding.

Common_Stock_and_Stockholders_

Common Stock and Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2014
Stockholders Equity Note [Abstract]
Common Stock and Stockholders' Equity (Deficit)	Note 12. Common Stock and Stockholders’ Equity (Deficit)
	Common Stock
	As of December 31, 2014, the Company is authorized to issue 5.0 billion shares of $0.000005 par value common stock in accordance with the Certificate of Incorporation, as amended and restated.
	Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when and if declared by the Board of Directors, subject to the prior rights of holders of all classes of stock outstanding. As of December 31, 2014, no dividends have been declared.
	Restricted Common Stock
	The Company has granted restricted common stock to certain continuing employees in connection with the acquisitions. Vesting of this stock is dependent on the respective employee’s continued employment at the Company during the requisite service period, which is generally two to four years from the issuance date, and the Company has the right to repurchase the unvested shares upon termination of employment. The fair value of the restricted common stock issued to employees is recorded as compensation expense on a straight-line basis over the requisite service period.
	The activities for the restricted common stock issued to employees for the year ended December 31, 2014 are summarized as follows (in thousands, except per share data):
						Weighted-Average
			Number of			Grant-Date Fair
			Shares			Value Per Share
	Unvested restricted common stock at December 31, 2013			6,866		$	17.6
	Granted			2,468		$	33.8
	Vested			(3,956	)	$	17.68
	Canceled			(423	)	$	17.31
	Unvested restricted common stock at December 31, 2014			4,955		$	25.62
	In the years ended December 31, 2014, 2013 and 2012, the Company recorded $63.9 million, $31.7 million and $6.3 million, respectively, of compensation expense related to restricted common stock issued to employees. As of December 31, 2014, there was $93.5 million of unamortized stock-based compensation expense related to restricted common stock issued which is expected to be recognized over a weighted-average period of 2.43 years.
	Equity Incentive Plans
	The Company’s 2013 Equity Incentive Plan became effective upon the completion of the Company’s initial public offering and serves as the successor to the 2007 Equity Incentive Plan. Initially, 68.3 million shares were reserved under the 2013 Equity Plan and any shares subject to options or other similar awards granted under the 2007 Equity Incentive Plan that expire, are forfeited, are repurchased by the Company or otherwise terminate unexercised will become available under the 2013 Equity Incentive Plan. The number of Shares available for issuance under the 2013 Equity Incentive Plan will be increased on the first day of each fiscal year beginning with the 2014 fiscal year, in an amount equal to the least of (i) 60,000,000 Shares, (ii) 5% of the outstanding Shares on the last day of the immediately preceding fiscal year or (iii) such number of Shares determined by the Company’s Board of Directors.  As of December 31, 2014, the total number of options and RSUs outstanding under the 2013 Equity Incentive Plan was 23.9 million shares, and 81.8 million shares were available for future issuance.  There were 59.1 million shares of options and RSUs outstanding under the 2007 Equity Incentive Plan as of December 31, 2014. No additional shares will be issued under the 2007 Equity Incentive Plan. Options granted under the Company’s Equity Incentive Plans generally expire 10 years after the grant date.  The Company issues new shares to satisfy stock option exercises.
	Under the 2007 Equity Incentive Plan, RSUs granted to domestic and international employees prior to February 2013 (“Pre-2013 RSUs”) vest upon the satisfaction of both a service condition and a performance condition. The service condition for these awards is generally satisfied over four years. RSUs granted to domestic employees starting in February 2013 (“Post-2013 RSUs”) are not subject to a performance condition in order to vest. The majority of Post-2013 RSUs vest over a service period of four years. Pursuant to the terms of the 2007 Equity Incentive Plan and the 2013 Equity Incentive Plan, the shares underlying Post-2013 RSUs that satisfy the service condition are to be delivered to holders no later than the fifteenth day of the third month following the end of the calendar year the service condition is satisfied, or if later, the end of the Company’s tax year. The Company undertook a net settlement of vested RSUs held by the executive officers upon settlement of their Pre-2013 RSUs in 2014, withheld shares and remitted income tax on behalf of the applicable executive officers of $17.1 million in cash at the applicable minimum statutory rates in the year ended December 31, 2014.  The shares that were withheld by the Company as a result of the net settlement of RSUs are no longer considered issued and outstanding.
	The Company also assumed stock options of acquired entities in connection with certain acquisitions. While the respective stock plans were terminated on the closing of each acquisition, they continue to govern the terms of stock options assumed in the respective acquisition. As of December 31, 2014, there were an aggregate of 1.6 million outstanding stock options assumed in these acquisitions.
	Employee Stock Purchase Plan
	On November 7, 2013, the Company’s 2013 Employee Stock Purchase Plan (the “ESPP”) became effective. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP provides for twelve-month offering periods, and each offering period will include purchase periods, which will be the approximately six-month period commencing with one exercise date and ending with the next exercise date.  Employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the exercise date.  The number of shares available for sale under the 2013 Employee Stock Purchase Plan will be increased annually on the first day of each fiscal year, equal to the least of i) 11.3 million shares; ii) 1% of the outstanding shares of the Company’s common stock as of the last day of the immediately preceding fiscal year; or iii) such other amount as determined by the Board of Directors.
	During the year ended December 31, 2014, employees purchased an aggregate of 1.9 million shares under this plan at a weighted average price of $22.47 per share. As of December 31, 2014, 15.8 million shares were available for future issuance under the ESPP. During the years ended December 31, 2014 and 2013, the Company recorded $31.8 million and $5.4 million of stock-based compensation expense, respectively, related to the ESPP.
	Stock Option Activity
	A summary of stock option activity for the year ended December 31, 2014 is as follows (in thousands, except years and per share data):
			Options Outstanding
									Weighted-
						Weighted-			Average
						Average			Remaining
			Number of			Exercise			Contractual Life			Aggregate
			Shares			Price Per Share			(in years)			Intrinsic Value
	Outstanding at December 31, 2013			42,246		$	1.89			6.47		$	2,609,295
	Options granted			500		$	42.05
	Options assumed in connection with acquisitions			819		$	1.6
	Options exercised			(22,447	)	$	1.29
	Options canceled			(698	)	$	7.27
	Outstanding at December 31, 2014			20,420		$	3.33			5.78		$	667,538
	Vested and expected to vest at			20,097		$	3.18			5.75		$	659,695
	December 31, 2014 (1)
	Exercisable at December 31, 2014			17,295		$	1.65			5.44		$	591,755
	-1	The expected to vest options are the result of applying pre-vesting forfeiture rate assumptions to unvested options outstanding.
	The aggregate intrinsic value in the table above represents the difference between the fair value of common stock and the exercise price of outstanding, in-the-money stock options.
	The total intrinsic values of stock options exercised in the years ended December 31, 2014, 2013 and 2012 were $872.8 million, $123.7 million and $84.6 million, respectively.
	RSU Activity
	The following table summarizes the activity related to the Company’s Pre-2013 and Post-2013 RSUs for the year ended December 31, 2014.  For purposes of this table, vested RSUs represent the shares for which the service condition had been fulfilled as of each respective date (in thousands, except per share data):
			RSUs Outstanding
						Weighted-
						Average Grant-
						Date Fair Value
			Shares			Per Share
	Unvested and outstanding at December 31, 2013			79,876		$	19.54
	Granted			24,409		$	48.49
	Vested			(26,903	)	$	21.34
	Canceled			(13,247	)	$	23.02
	Unvested and outstanding at December 31, 2014			64,135		$	29.08
	The total fair value of RSUs vested during the year ended December 31, 2014 was approximately $1.13 billion.  In addition, the total fair value of Pre-2013 RSUs vested during the year ended December 31, 2014, for which the service condition had been fulfilled prior to January 1, 2014, was approximately $888.1 million.
	Stock-Based Compensation Expense
	Stock-based compensation expense is allocated based on the cost center to which the award holder belongs. Total stock-based compensation expense by function for the years ended December 31, 2014, 2013 and 2012 is as follows (in thousands):
			Year Ended December 31,
			2014			2013			2012
	Cost of revenue		$	50,536		$	50,942		$	800
	Research and development			360,726			379,913			12,622
	Sales and marketing			157,263			114,440			1,346
	General and administrative			63,072			55,072			10,973
Total		$	631,597		$	600,367		$	25,741
Upon completion of the Company’s initial public offering in November 2013, the Company began recording stock-based compensation expense related to Pre-2013 RSUs because the satisfaction of the performance condition for vesting became probable.  During the year ended December 31, 2013, the amount of stock-based compensation expense recorded in relation to Pre-2013 RSUs totaled approximately $433.5 million and was comprised of $405.9 million of expense accumulated until the effective date of the initial public offering for awards vested and $27.6 million of subsequent recognition of expense during the year as additional Pre-2013 RSUs continued to vest. During the year ended December 31, 2014, the Company recorded $84.4 million of expense in relation to Pre-2013 RSUs as the stock-based compensation continued to be amortized for outstanding Pre-2013 RSUs on an accelerated basis.
The Company modified the terms of stock options and RSUs for certain employees upon their termination or change in employment status. The Company recorded incremental stock-based compensation in relation to the modification of stock-based awards of approximately $32.6 million in the year ended December 31, 2014. The amount of incremental stock-based compensation recorded in relation to the modification of stock-based awards was not material for the years ended December 31, 2013 and 2012, respectively.
Income tax benefits recognized for stock-based compensation arrangements during the years ended December 31, 2014, 2013 and 2012 were not material.
The Company capitalized $40.8 million, $13.6 million and $1.3 million of stock-based compensation expense associated with the cost for developing software for internal use in the years ended December 31, 2014, 2013 and 2012, respectively.
The weighted-average grant-date fair value of stock options granted to employees and assumed in connection with acquisitions in the years ended December 31, 2014, 2013 and 2012 was $30.12, $11.89 and $7.42 per share, respectively. The fair value of stock options granted to employees was determined using the Black-Scholes option pricing model with the following weighted-average assumptions:
		Year Ended December 31,
		2014			2013			2012
Expected dividend yield			—			—			—
Risk-free interest rate			1.47	%		1.24	%		1.3	%
Expected volatility			42.54	%		52.14	%		51.79	%
Expected term (in years)			4.73			5.37			6.56
As of December 31, 2014, there was $33.3 million of unamortized stock-based compensation expense related to unvested stock options granted to employees and non-employee service providers which is expected to be recognized over a weighted-average period of 2.25 years. The unamortized stock-based compensation expense related to Pre-2013 and Post-2013 RSUs of $48.6 million and $1.26 billion, respectively, as of December 31, 2014 is expected to be recognized over a weighted-average period of 1.79 years and 2.91 years, respectively. An amount of $15.4 million of unamortized stock-based compensation expense related to the ESPP is expected to be recognized over a period of 0.85 years.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Note 13. Income Taxes
	The domestic and foreign components of pre-tax loss for the years ended December 31, 2014, 2013 and 2012 are as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Domestic	$	(164,854	)	$	(549,397	)	$	(53,699	)
	Foreign		(413,497	)		(97,749	)		(25,471	)
	Loss before income taxes	$	(578,351	)	$	(647,146	)	$	(79,170	)
	The components of the provision (benefit) for income taxes for the years ended December 31, 2014, 2013 and 2012 are as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Current:
	Federal	$	—		$	—		$	—
	State		720			857			(300	)
	Foreign		8,358			6,222			1,627
	Total current provision for income taxes		9,078			7,079			1,327
	Deferred:
	Federal		(8,972	)		(5,412	)		(608	)
	State		(128	)		(453	)		(89	)
	Foreign		(509	)		(3,037	)		(401	)
	Total deferred benefit for income taxes		(9,609	)		(8,902	)		(1,098	)
	Provision (benefit) for income taxes	$	(531	)	$	(1,823	)	$	229
	The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate for the years ended December 31, 2014, 2013 and 2012:
		Year Ended December 31,
		2014			2013			2012
	Tax at federal statutory rate		35	%		35	%		35	%
	State taxes, net of federal benefit		(0.1	)		(0.1	)		0.5
	Stock-based compensation		(4.2	)		(2.9	)		(1.9	)
	Research and development credits		25.2			3.6			—
	Valuation Allowance		(9.4	)		(25.0	)		(10.1	)
	Nondeductible expenses		(4.5	)		(3.0	)		(8.7	)
	Foreign rate differential		(26.4	)		(5.8	)		(12.7	)
	Change in tax positions		(15.9	)		(2.0	)		(2.8	)
	Other		0.4			0.5			0.4
	Effective tax rate		0.1	%		0.3	%		(0.3	)%
	The tax effects of temporary differences and related deferred tax assets and liabilities as of December 31, 2014 and 2013 are as follows (in thousands):
		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carryforwards	$	230,417		$	82,719
	Accruals and reserves		20,496			11,435
	Stock-based compensation expense		89,159			195,338
	Research and development credits		168,934			28,572
	California Enterprise Zone Credit		10,355			8,163
	Other		3,145			1,131
	Total deferred tax assets		522,506			327,358
	Valuation allowance		(351,249	)		(227,878	)
	Total deferred tax assets, net of valuation allowance		171,257			99,480
	Deferred tax liabilities:
	Fixed assets and intangible assets		(132,671	)		(80,072	)
	Convertible notes		(35,133	)		—
	Other		(420	)		(457	)
	Total deferred tax liabilities		(168,224	)		(80,529	)
	Net deferred tax assets	$	3,033		$	18,951
	Based on the available objective evidence, management believes it is more-likely-than-not that the net U.S. deferred tax assets were not fully realizable as of the year ended December 31, 2014. Accordingly, the Company has established a full valuation allowance against its U.S. deferred tax assets. As of December 31, 2014, the Company has net $3.2 million of deferred tax assets in foreign jurisdictions which it believes are more-likely-than-not to be fully realized given the expectation of future earnings in these jurisdictions.
	For the year ended December 31, 2014, the Company has not provided for income taxes on $42.9 million of its undistributed earnings for certain foreign subsidiaries because these earnings are intended to be permanently reinvested in operations outside the U.S. Determining the unrecognized deferred tax liabilities associated with these earnings is not practicable.
	At December 31, 2014, the Company had $2.60 billion of federal and $1.00 billion of state net operating loss carryforwards available to reduce future taxable income, which will begin to expire in 2027 for federal and 2015 for state tax purposes.
	Pursuant to authoritative guidance, the excess tax benefit from stock-based compensation will only be recorded to stockholders’ equity when cash taxes payable are reduced. As of December 31, 2014, the portion of net operating loss carryforwards related to the excess tax benefit from stock-based compensation is approximately $2.49 billion, the benefit of which will be credited to additional paid-in capital when realized.
	The Company also has research credit carryforwards of $175.9 million and $142.0 million for federal and state income tax purposes, respectively. The federal credit carryforward will begin to expire in 2027. The state research tax credits have no expiration date. Additionally, the Company has California Enterprise Zone Credit carryforwards of $15.9 million which will begin to expire in 2023.
	Utilization of the net operating loss carryforwards and credits may be subject to an annual limitation due to the ownership change limitations provided by the Internal Revenue Code of 1986, as amended (the “Code”), and similar state provisions. Any annual limitation may result in the expiration of net operating losses and credits before utilization.
	As of December 31, 2014, the unrecognized tax benefit was $182.5 million, materially all of which would result in corresponding adjustments to valuation allowance. A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Balance at the beginning of the year	$	43,061		$	23,352		$	25,845
	Additions related to prior year tax positions		—			7,880			—
Reductions related to prior year tax positions		(50	)		—			(3,612	)
Additions related to current year tax positions		139,473			11,829			1,119
Balance at the end of the year	$	182,484		$	43,061		$	23,352
Total unrecognized tax benefits are recorded on the Company’s consolidated balance sheets as follows (in thousands):
	December 31,
	2014			2013
Total unrecognized tax benefits balance	$	182,484		$	43,061
Amounts netted against related deferred tax assets		(181,786	)		(27,160	)
Unrecognized tax benefits recorded on consolidated balance sheets	$	698		$	15,901
The net unrecognized tax benefit of $0.7 million and $15.9 million as of December 31, 2014 and 2013, respectively, was included in the deferred and other long-term tax liabilities, net on the Company’s consolidated balance sheets. The Company adopted new guidance on the financial statement presentation of unrecognized tax benefits prospectively as of January 1, 2014. The application of this guidance resulted in a $15.8 million decrease in net deferred tax assets and the related liability for unrecognized tax benefits upon adoption. The Company does not believe that its unrecognized tax benefits will significantly change within the next 12 months.
The Company recognizes interest and/or penalties related to income tax matters as a component of income tax expense. As of December 31, 2014 there were no significant accrued interest and penalties related to uncertain tax positions.
The Company is subject to taxation in the United States and various state and foreign jurisdictions. Earnings from non-US activities are subject to local country income tax. The material jurisdictions in which the Company is subject to potential examination by taxing authorities include the United States, California and Ireland. The Company is currently under a Federal income tax examination by the Internal Revenue Service (IRS) for tax years 2011 and 2012 and under examination in California for tax years 2010 and 2011. The Company believes that adequate amounts have been reserved in these jurisdictions. The Company’s 2007 to 2014 tax years remain subject to examination by the United States and California, and its 2011 to 2014 tax years remain subject to examination in Ireland. The Company remains subject to possible examination in various other jurisdictions that are not expected to result in material tax adjustments.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 14. Commitments and Contingencies
	Credit Facility
	The Company entered into a revolving credit agreement with certain lenders in 2013, which provided for a $1.0 billion revolving unsecured credit facility maturing on October 22, 2018. Loans under the credit facility bear interest, at the Company’s option, at (i) a base rate based on the highest of the prime rate, the federal funds rate plus 0.50% and an adjusted LIBOR rate for a one-month interest period plus 1.00%, in each case plus a margin ranging from 0.00% to 0.75% or (ii) an adjusted LIBOR rate plus a margin ranging from 1.00% to 1.75%. This margin is determined based on the total leverage ratio for the preceding four fiscal quarter period. The Company is obligated to pay other customary fees for a credit facility of this size and type, including an upfront fee and an unused commitment fee. Obligations under the credit facility are guaranteed by one of the Company’s wholly-owned subsidiaries. In addition, the credit facility contains restrictions on payments including cash payments of dividends.
	The revolving credit agreement was amended in September 2014 to increase the amount of indebtedness that the Company may incur and increase the amount of restricted payments that the Company may make. This amendment to the revolving credit agreement also provides that if the Company’s total leverage ratio exceeds 2.5:1.0 and if the amount outstanding under the credit facility exceeds $500.0 million, or 50% of the amount that may be borrowed under the credit facility, the credit facility will become secured by substantially all of the Company’s and certain of its subsidiaries’ assets, subject to limited exceptions. As of December 31, 2014, no amounts were drawn under the credit facility.
	Operating and Capital Leases
	The Company has entered into various non-cancelable operating lease agreements for certain offices and data center facilities with contractual lease periods expiring between 2015 and 2026. In 2014, the Company entered into various lease amendments for additional office space for its headquarters through 2026 with a total remaining lease commitment of $233.3 million as of December 31, 2014. Under the terms of the lease, as amended, the Company is responsible for certain taxes, insurance, maintenance and management expenses.
	In addition, in 2014 the Company entered into a lease agreement for an additional data center facility and lease amendments for capacity expansion of existing data center facilities through 2023 and increased the total commitments to $464.5 million as of December 31, 2014.
	A summary of gross and net lease commitments as of December 31, 2014 is as follows (in thousands):
		Operating		Capital
		Leases		Leases
	Years ending December 31,
	2015	$	110,221	$	119,771
	2016		135,625		81,758
	2017		138,663		38,818
	2018		134,667		4,159
	2019		102,932		—
	Thereafter		296,371		—
		$	918,479		244,506
	Less: Amounts representing interest				13,236
	Total capital lease obligation				231,270
	Less: Short-term portion				112,320
	Long-term portion			$	118,950
	Rent expense under the Company’s operating leases, including co-location arrangements for the Company’s data centers, was $73.9 million, $35.4 million and $19.4 million for the years ended December 31, 2014, 2013 and 2012, respectively. The Company also had $38.9 million of non-cancelable contractual commitments as of December 31, 2014, primarily related to its bandwidth and other services arrangements. These commitments are generally due within one to two years.
	Legal Proceedings
	The Company is currently involved in, and may in the future be involved in, legal proceedings, claims and governmental investigations in the normal course of business. Legal fees and other costs associated with such actions are expensed as incurred. The Company assesses, in conjunction with its legal counsel, the need to record a liability for litigation and contingencies. Litigation accruals are recorded when and if it is determined that a loss related matter is both probable and reasonably estimable. Material loss contingencies that are reasonably possible of occurrence, if any, are subject to disclosure. As of December 31, 2014, there was no litigation or contingency with at least a reasonable possibility of a material loss. No material losses have been recorded during years ended December 31, 2014, 2013 and 2012 with respect to litigation or loss contingencies.
	Indemnification
	In the ordinary course of business, the Company often includes standard indemnification provisions in its arrangements with its customers, partners, suppliers and vendors. Pursuant to these provisions, the Company may be obligated to indemnify such parties for losses or claims suffered or incurred in connection with its service, breach of representations or covenants, intellectual property infringement or other claims made against such parties. These provisions may limit the time within which an indemnification claim can be made. It is not possible to determine the maximum potential amount under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement. The Company has never incurred significant expense defending its licensees against third party claims, nor has it ever incurred significant expense under its standard service warranties or arrangements with its customers, partners, suppliers and vendors. Accordingly, the Company had no liabilities recorded for these provisions as of December 31, 2014 and 2013.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related Party Transactions	Note 15. Related Party Transactions
	One of the Company’s directors has a direct ownership interest in a vendor that provides marketing and communication services to the Company. For the years ended December 31, 2014 and 2013, no expenses were incurred for services rendered.  For the year ended December 31, 2012, the Company incurred $1.9 million of expense for services rendered. There was no outstanding payable balance associated with the vendor as of December 31, 2014.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	Note 16. Employee Benefit Plan
	The Company adopted a 401(k) Plan that qualifies as a deferred compensation arrangement under Section 401 of the Code. Under the 401(k) Plan, participating employees may defer a portion of their pretax earnings not to exceed the maximum amount allowable. The Company has not made any matching contributions to date.

Segment_Information_and_Operat

Segment Information and Operations by Geographic Area	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Information and Operations by Geographic Area	Note 17. Segment Information and Operations by Geographic Area
	The Company has a single operating segment and reporting unit structure. The Company’s chief operating decision-maker is the chief executive officer who reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenue by geographic region for purposes of allocating resources and evaluating financial performance.
	Revenue
	Revenue by geography is based on the billing addresses of the customers. The following tables set forth revenue by services and revenue by geographic area (in thousands):
		Year Ended December 31,
		2014		2013		2012
		(in thousands)
	Advertising services	$	1,255,688	$	594,546	$	269,421
	Data licensing and other		147,314		70,344		47,512
	Total Revenue	$	1,403,002	$	664,890	$	316,933
		Year Ended December 31,
		2014		2013		2012
	Revenue:
	United States	$	945,720	$	492,320	$	263,917
	International		457,282		172,570		53,016
	Total revenue	$	1,403,002	$	664,890	$	316,933
	The United Kingdom accounted for $140.3 million and $66.5 million or 10% and 10% of the total revenue for the years ended December 31, 2014 and 2013, respectively. No individual country from the international markets contributed in excess of 10% of the total revenue for the year ended December 31, 2012.
	Property and Equipment, net
	The following table sets forth property and equipment, net by geographic area (in thousands):
		December 31,		December 31,
		2014		2013
	Property and equipment, net:
	United States	$	523,810	$	327,250
	International		33,209		5,412
	Total property and equipment, net	$	557,019	$	332,662

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Valuation And Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	PART IV
	Item 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES
	The following documents are filed as part of this Annual Report on Form 10-K:
	1	Consolidated Financial Statements
	Our Consolidated Financial Statements are listed in the “Index to Consolidated Financial Statements” under Part II, Item 8 of this Annual Report on Form 10-K.
	2	Financial Statement Schedules
	SCHEDULE II
	VALUATION AND QUALIFYING ACCOUNTS
	FOR THE YEARS ENDED DECEMBER 31, 2014, 2013 AND 2012
						Charged/
		Balance at				Credited
		Beginning of		Charged to		to Other			Balance at
		Year		Expenses		Accounts			End of Year
		(In thousands)
	Allowance for Deferred Tax Assets:
	Year ended December 31, 2014	$	227,878	$	155,111	$	(31,740	)	$	351,249
	Year ended December 31, 2013	$	42,175	$	180,691	$	5,012		$	227,878
	Year ended December 31, 2012	$	24,895	$	15,250	$	2,030		$	42,175
		Balance at
		Beginning of		Additions		Write-off/			Balance at
		Year		(Reductions)		Adjustments			End of Year
		(In thousands)
	Allowance for Doubtful Accounts:
	Year ended December 31, 2014	$	2,020	$	4,632	$	(1,145	)	$	5,507
	Year ended December 31, 2013	$	1,280	$	1,557	$	(817	)	$	2,020
	Year ended December 31, 2012	$	1,828	$	1,844	$	(2,392	)	$	1,280
	All other financial statement schedules have been omitted because they are not required, not applicable, not present in amounts sufficient to require submission of the schedule, or the required information is shown in our Consolidated Financial Statements or Notes thereto.
	3	Exhibits
	The documents listed in the Exhibit Index of this Annual Report on Form 10-K are incorporated by reference or are filed with this Annual Report on Form 10-K, in each case as indicated therein (numbered in accordance with Item 601 of Regulation S-K).

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates
	The preparation of the Company’s consolidated financial statements in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, as well as related disclosure of contingent assets and liabilities. Actual results could differ materially from the Company’s estimates. To the extent that there are material differences between these estimates and actual results, the Company’s financial condition or operating results will be affected. The Company bases its estimates on past experience and other assumptions that the Company believes are reasonable under the circumstances, and the Company evaluates these estimates on an ongoing basis.
Revenue Recognition	Revenue Recognition
	The Company generates revenue principally from the sale of advertising services and, to a lesser extent, from entering into data licensing and other arrangements. The Company’s advertising services include three primary products: (i) Promoted Tweets, (ii) Promoted Accounts and (iii) Promoted Trends. Promoted Tweets and Promoted Accounts are pay-for-performance advertising products priced through an auction. Promoted Trends are featured by geography and offered on a fixed-fee-per-day basis. Advertisers are obligated to pay when a user engages with a Promoted Tweet or follows a Promoted Account or when a Promoted Trend is displayed. Users engage with Promoted Tweets by clicking on a link in a Promoted Tweet, expanding, retweeting, favoriting or replying to a Promoted Tweet or following the account that tweets a Promoted Tweet. These products may be sold in combination as a multiple element arrangement or separately on a stand-alone basis. Fees for these advertising services are recognized in the period when advertising is delivered as evidenced by a user engaging with a Promoted Tweet, as captured by a click, following a Promoted Account or through the display of a Promoted Trend on the Company’s platform. Data licensing revenue is generated based on monthly service fees charged to the data partners over the period in which the Company’s data and data products are made available to them. Other revenue is primarily generated from service fees from transactions completed on the mobile ad exchange. The Company’s mobile ad exchange enables buyers and sellers to purchase and sell advertising inventory and matches buyers and sellers. The Company has determined it is not the principal in the purchase and sale of advertising inventory in transactions between third party buyers and sellers on the exchange. Therefore, the Company reports revenue related to its ad exchange services on a net basis.
	Revenue is recognized only when (1) persuasive evidence of an arrangement exists; (2) the price is fixed or determinable; (3) the service is performed; and (4) collectability of the related fee is reasonably assured. While the majority of the Company’s revenue transactions are based on standard business terms and conditions, the Company also enters into non-standard sales agreements with advertisers and data partners that sometimes involve multiple elements.
	For arrangements involving multiple deliverables, judgment is required to determine the appropriate accounting, including developing an estimate of the stand-alone selling price of each deliverable. When neither vendor-specific objective evidence nor third-party evidence of selling price exists, the Company uses its best estimate of selling price (BESP) to allocate the arrangement consideration on a relative selling price basis to each deliverable. The objective of BESP is to determine the selling price of each deliverable when it is sold to advertisers on a stand-alone basis. In determining BESPs, the Company takes into consideration various factors, including, but not limited to, prices the Company charges for similar offerings, sales volume, geographies, pricing strategies and market conditions. Multiple deliverable arrangements primarily consist of combinations of the Company’s pay-for-performance products, Promoted Tweets and Promoted Accounts, which are priced through an auction, and Promoted Trends, which are priced on a fixed-fee-per day per geography basis. For arrangements that include a combination of these products, the Company develops an estimate of the selling price for these products in order to allocate any potential discount to all advertising products in the arrangement. The estimate of selling price for pay-for-performance products is determined based on the winning bid price; the estimate of selling price for Promoted Trends is based on Promoted Trends sold on a stand-alone basis and/or separately priced in a bundled arrangement by reference to a list price by geography which is approved periodically. The Company believes the use of BESP results in revenue recognition in a manner consistent with the underlying economics of the transaction and allocates the arrangement consideration on a relative selling price basis to each deliverable.
Cost of Revenue	Cost of Revenue
	Cost of revenue consists primarily of data center costs related to the Company’s co-located facilities, which includes lease and hosting costs, related support and maintenance costs and energy and bandwidth costs, as well as depreciation of its servers and networking equipment, networking costs and personnel-related costs, including salaries, benefits and stock-based compensation, for its operations teams. Cost of revenue also includes allocated facilities and other supporting overhead costs, amortization expense of technology acquired through acquisitions and capitalized labor costs.
Stock-Based Compensation Expense	Stock-Based Compensation Expense
	The Company accounts for stock-based compensation expense under the fair value recognition and measurement provisions of U.S. GAAP. Stock-based awards granted to employees are measured based on the grant-date fair value with the resulting expense recognized over the respective period during which the award recipient is required to provide service.
	Pre-2013 RSUs, as defined and further described in Note 12—Common Stock and Stockholders’ Equity (Deficit), vest upon satisfaction of both a service condition and a performance condition. The service condition for these awards is generally satisfied over four years. The performance condition was satisfied in February 2014 pursuant to the terms of the Company’s 2007 Equity Incentive Plan. Prior to the closing of the Company’s initial public offering in November 2013, the Company had not recognized any stock-based compensation expense for the Pre-2013 RSUs, because the performance condition had not been satisfied. As the satisfaction of the performance condition became probable upon completion of the Company’s initial public offering for the Pre-2013 RSUs for which the service condition had been satisfied as of such date, the Company recorded the cumulative stock-based compensation expense for these RSUs during the three months ended December 31, 2013, using the accelerated attribution method. The remaining unrecognized stock-based compensation expense related to the Pre-2013 RSUs will be recorded over the remaining requisite service period using the accelerated attribution method.
	Post-2013 RSUs, as defined and further described in Note 12—Common Stock and Stockholders’ Equity (Deficit), are not subject to a performance condition in order to vest. The service condition for these awards is generally satisfied over four years. The compensation expense related to these RSUs is recognized on a straight-line basis over the requisite service period.
	The Company estimates the fair value of stock options granted and stock purchase rights provided under the Company’s employee stock purchase plan using the Black-Scholes option pricing model on the dates of grant. Calculating the fair value using the Black-Scholes model requires various judgmental assumptions including the expected term and stock price volatility. The Company estimates the expected term of stock options granted based on the simplified method. The Company estimates the expected volatility of its common stock on the dates of grant based on a combination of the Company’s historical stock price volatility and implied volatility in the Company’s traded options when such information is available. When the Company’s historical and implied volatility data are not available for the related awards’ expected term, an average of volatility rates including the historical volatility of a group of comparable, publicly-traded companies is used. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Expected dividend yield is zero percent as the Company has not paid and does not anticipate paying dividends on its common stock. The compensation expense related to stock options and employee stock purchase rights is recognized on a straight-line basis over the requisite service period.
	The Company issues restricted stock subject to a lapsing right of repurchase to continuing employees of certain acquired companies. Since these issuances are subject to post-acquisition employment, the Company accounts for them as post-acquisition stock-based compensation expense. The grant-date fair value of restricted stock granted in connection with acquisitions is recognized as stock-based compensation expense on a straight-line basis over the requisite service period.
	Stock-based compensation expense is recorded net of estimated forfeitures. The Company estimates the forfeiture rate based on historical forfeitures of stock-based awards and adjusts the rate to reflect changes in facts and circumstances, if any.
Acquisitions	Acquisitions
	The Company accounts for acquisitions of entities that include inputs and processes and have the ability to create outputs as business combinations in accordance with Accounting Standards Codification (“ASC”) Topic 805 Business Combinations. The purchase price of the acquisition is allocated to the tangible and intangible assets acquired and liabilities assumed based on their estimated fair values at the acquisition dates. The excess of the purchase price over those fair values is recorded as goodwill. During the measurement period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the consolidated statements of operations.
	Costs to exit or restructure certain activities of an acquired company or the Company’s internal operations are accounted for as one-time termination and exit costs and are accounted for separately from the business combination. Restructuring and other acquisition-related costs are expensed as incurred.
Operating and Capital Leases	Operating and Capital Leases
	The Company leases office space and data center facilities under operating leases. Certain lease agreements contain free or escalating rent payment provisions. The Company recognizes rent expense under such leases on a straight-line basis over the term of the lease. Lease renewal periods are considered on a lease-by-lease basis in determining the lease term.
	The Company also enters into server and networking equipment lease arrangements with original lease terms ranging from two to four years. The classification of each lease arrangement is determined in accordance with the criteria outlined in ASC Topic 840 Leases. The Company’s server and networking equipment leases typically are accounted for as capital leases as they meet one or more of the four capital lease classification criteria. Assets acquired under capital leases are amortized over the shorter of the remaining lease term or their estimated useful life. As of December 31, 2014 and 2013, the Company had capital lease obligations included in short-term and long-term capital lease obligations in the consolidated balance sheets of $231.3 million and $197.6 million, respectively. In the years ended December 31, 2014, 2013 and 2012, the Company recorded approximately $10.2 million, $7.0 million and $3.1 million, respectively, of interest expense in relation to these capital lease arrangements.
Cash, Cash Equivalents and Investments	Cash, Cash Equivalents and Investments
	The Company invests its excess cash primarily in short-term interest-bearing obligations, including government and investment-grade debt securities and money market funds. The Company classifies all liquid investments with stated maturities of three months or less from date of purchase as cash equivalents.  The Company classifies investments with stated maturities of greater than three months and less than 12 months from the date of purchase as short-term investments and those with stated maturities of 12 months or greater as long-term investments in the consolidated balance sheets. As of December 31, 2014 and 2013, the Company did not hold any long-term investments. As of December 31, 2014 and 2013, the Company has recorded restricted cash balances of $2.6 million and $4.9 million, respectively, within prepaid expenses and other current assets and $28.3 million and $15.3 million, respectively, in other assets on the accompanying consolidated balance sheets based upon the term of the remaining restrictions. These restricted cash balances are primarily related to certain operating lease arrangements.
	The Company determines the appropriate classification of its investments in marketable securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its marketable securities as available-for-sale. After considering the Company’s capital preservation objectives, as well as its liquidity requirements, the Company may sell securities prior to their stated maturities. The Company carries its available-for-sale securities at fair value, and reports the unrealized gains and losses, net of taxes, as a component of stockholders’ equity (deficit), except for unrealized losses determined to be other than temporary which are recorded as other income (expense), net. The Company determines any realized gains or losses on the sale of marketable securities on a specific identification method and records such gains and losses as a component of other income (expense), net. Interest earned on investments in marketable securities was $1.9 million, $0.7 million, and $0.8 million during the years ended December 31, 2014, 2013 and 2012, respectively. These balances are recorded in interest income (expense), net in the accompanying consolidated statements of operations.
	The Company evaluates the investments periodically for possible other-than-temporary impairment. A decline in fair value below the amortized costs of debt securities is considered an other-than-temporary impairment if the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the entire amortized cost basis. In those instances, an impairment charge equal to the difference between the fair value and the amortized cost basis is recognized in earnings. Regardless of the Company’s intent or requirement to sell a debt security, impairment is considered other-than-temporary if the Company does not expect to recover the entire amortized cost basis.
Concentration of Credit Risk	Concentration of Credit Risk
	Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. The primary focus of the Company’s investment strategy is to preserve capital and meet liquidity requirements. The Company’s investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, the Company invests cash, cash equivalents and short-term investments in a variety of fixed income securities, including short-term interest-bearing obligations, including government and investment-grade debt securities and money market funds. The Company places its cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any.
	The Company’s accounts receivable are typically unsecured and are derived from customers around the world in different industries. The Company performs ongoing credit evaluations of its customers and maintains allowances for potential credit losses. Historically, such losses have been within management’s expectations. As of December 31, 2014 and 2013, no single customer accounted for more than 10% of the Company’s net accounts receivable balance. No single customer accounted for more than 10% of the Company’s revenue in the years ended December 31, 2014, 2013 and 2012.
	The Company’s note hedge transactions, entered into in connection with the Notes, expose the Company to credit risk to the extent that its counterparties may be unable to meet the terms of the transactions. The Company mitigates this risk by limiting its counterparties to major financial institutions.
Accounts Receivable, Net	Accounts Receivable, Net
	The Company records accounts receivable at the invoiced amount. The Company maintains an allowance for doubtful accounts to reserve for potentially uncollectible receivable amounts. In evaluating the Company’s ability to collect outstanding receivable balances, the Company considers various factors including the age of the balance, the creditworthiness of the customer, which is assessed based on ongoing credit evaluations and payment history, and the customer’s current financial condition.
Property and Equipment, Net	Property and Equipment, Net
	Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets. Assets acquired under capital leases and leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful life. The estimated useful lives of property and equipment are described below:
	Property and Equipment	Estimated Useful Life
	Computer hardware and networking equipment	Two to four years
	Computer software	One to three years
	Office equipment and other	Five years
	Leased equipment and leasehold improvements	Lesser of estimated useful life or remaining lease term
	Costs of maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. Upon retirement or sale, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is reflected in operating expenses.
Goodwill	Goodwill
	Goodwill represents the excess of the purchase price over the fair value of the net tangible and intangible assets acquired in a business combination. Goodwill is not amortized, but is tested for impairment at least annually or more frequently if events or changes in circumstances indicate that the asset may be impaired. The Company’s impairment tests are based on a single operating segment and reporting unit structure. If the carrying value of the reporting unit exceeds its fair value, the second step of the test is performed by comparing the carrying value of the goodwill in the reporting unit to its implied fair value. An impairment charge is recognized for the excess of the carrying value of goodwill over its implied fair value.
	The Company conducted its annual goodwill impairment test during the fourth quarter of 2014 and determined that goodwill was not impaired. As such, no impairment charge was recorded in any of the periods presented in the accompanying consolidated financial statements.
Intangible Assets	Intangible Assets
	Intangible assets are carried at cost and amortized on a straight-line basis over their estimated useful lives, which range from one to eleven years. The Company reviews identifiable amortizable intangible assets to be held and used for impairment whenever events or changes in circumstances indicate that the carrying value of the assets may not be recoverable. Determination of recoverability is based on the lowest level of identifiable estimated undiscounted cash flows resulting from use of the asset and its eventual disposition. Measurement of any impairment loss is based on the excess of the carrying value of the asset over its fair value. There has been no impairment charges recorded in any of the periods presented in the accompanying consolidated financial statements. See Note 6—Goodwill and Intangible Assets for additional information.
Fair Value Measurements	Fair Value Measurements
	The Financial Accounting Standards Board (the “FASB”)’s authoritative guidance on fair value measurements establishes a framework for measuring fair value and requires disclosure about the fair value measurements of assets and liabilities. This guidance requires the Company to classify and disclose assets and liabilities measured at fair value on a recurring basis, as well as fair value measurements of assets and liabilities measured on a nonrecurring basis in periods subsequent to initial measurement, in a three-tier fair value hierarchy as described below.
	The guidance defines fair value as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The guidance describes three levels of inputs that may be used to measure fair value:
	Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities.
	Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
Internal Use Software and Website Development Costs	Internal Use Software and Website Development Costs
	The Company capitalizes certain costs incurred in developing software programs or websites for internal use. In the years ended December 31, 2014, 2013 and 2012, the Company capitalized costs totaling approximately $79.5 million, $35.6 million and $11.6 million, respectively. The estimated useful life of costs capitalized is evaluated for each specific project and is one to three years. In the years ended December 31, 2014, 2013 and 2012, the amortization of capitalized costs included in cost of revenue totaled approximately $15.2 million, $6.7 million and $5.6 million, respectively. Capitalized internal use software development costs are included in property and equipment, net. Included in the capitalized amounts above are $40.8 million, $13.6 million and $1.3 million of stock-based compensation expense in the years ended December 31, 2014, 2013 and 2012, respectively.
Income Taxes	Income Taxes
	The Company accounts for its income taxes using the asset and liability method whereby deferred tax assets and liabilities are determined based on temporary differences between the bases used for financial reporting and income tax reporting purposes, as well as for operating loss and tax credit carryforwards. Deferred income taxes are provided based on the enacted tax rates expected to be in effect at the time such temporary differences are expected to reverse. A valuation allowance is provided for deferred tax assets if it is more-likely-than-not that the Company will not realize those tax assets through future operations.
	The Company evaluates and accounts for uncertain tax positions using a two-step approach. Recognition (step one) occurs when the Company concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustainable upon examination. Measurement (step two) determines the amount of benefit that is greater than 50% likely to be realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. De-recognition of a tax position that was previously recognized would occur when the Company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained.
Foreign Currency	Foreign Currency
	The functional currency of the Company's foreign subsidiaries is generally the local currency. The financial statements of these subsidiaries are translated into U.S. dollars using period-end rates of exchange for assets and liabilities, historical rates of exchange for equity, and average rates of exchange for revenue and expenses. Translation gains (losses) are recorded in accumulated other comprehensive income (loss) as a component of stockholders’ equity. Other income (expense), net in the accompanying consolidated statements of operations consists primarily of unrealized foreign exchange gains and losses due to re-measurement of monetary assets and liabilities denominated in non-functional currencies as well as realized foreign exchange gains and losses on foreign exchange transactions.
Advertising Costs	Advertising Costs
	Advertising costs are expensed when incurred and are included in sales and marketing expense in the accompanying consolidated statements of operations. Advertising expense totaled $46.6 million, $3.1 million and $0.7 million for the years ended December 31, 2014, 2013 and 2012 respectively.
Comprehensive Loss	Comprehensive Loss
	Comprehensive loss consists of two components, net loss and other comprehensive income (loss). Other comprehensive income (loss) refers to gains and losses that are recorded as an element of stockholders’ equity and are excluded from net loss. The Company’s other comprehensive income (loss) is comprised of unrealized gains or losses on available-for-sale securities, net of tax, and foreign currency translation adjustment.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In May 2014, the FASB issued a new accounting standard update on revenue recognition from contracts with customers. The new guidance will replace all current U.S. GAAP guidance on this topic and eliminate all industry-specific guidance. According to the new guidance, revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration for which the Company expects to be entitled in exchange for those goods or services. This guidance will be effective for the Company beginning January 1, 2017 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is not permitted. The Company has not yet selected a transition method and is evaluating the impact of adopting this new accounting standard update on the financial statements and related disclosures.
	In June 2014, the FASB issued a new accounting standard update on stock-based compensation when the terms of an award provide that a performance target could be achieved after the requisite service period. The new guidance requires that a performance target that affects vesting, and that could be achieved after the requisite service period, be treated as a performance condition. As such, the performance target should not be reflected in estimating the grant-date fair value of the award. This update further clarifies that compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the periods for which the requisite service has already been rendered. This guidance will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015 and can be applied either prospectively or retrospectively to all awards outstanding as of the beginning of the earliest annual period presented as an adjustment to opening retained earnings. Early adoption is permitted. Adoption of this new accounting standard update is expected to have no impact to the Company’s financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Schedule of Estimated Useful Lives of Property and Equipment	The estimated useful lives of property and equipment are described below:
	Property and Equipment	Estimated Useful Life
	Computer hardware and networking equipment	Two to four years
	Computer software	One to three years
	Office equipment and other	Five years
	Leased equipment and leasehold improvements	Lesser of estimated useful life or remaining lease term

Cash_Cash_Equivalents_and_Shor1

Cash, Cash Equivalents and Short-term Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Cash And Cash Equivalents [Abstract]
Cash, Cash and Equivalents and Short-term Investments	Cash, cash equivalents and short-term investments consist of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Cash and cash equivalents:
	Cash	$	147,848	$	164,135
	Money market funds		882,443		229,529
	U.S. government and agency securities including treasury bills		271,418		251,593
	Corporate notes, certificates of deposit and commercial paper		209,015		195,753
	Total cash and cash equivalents	$	1,510,724	$	841,010
	Short-term investments:
	U.S. government and agency securities including treasury bills	$	1,009,541	$	785,536
	Corporate notes, certificates of deposit and commercial paper		1,101,613		607,508
	Total short-term investments	$	2,111,154	$	1,393,044
Summary of Unrealized Gains and Losses Related to Available-for-Sale Securities Classified as Short-term Investments	The following tables summarize unrealized gains and losses related to available-for-sale securities classified as short-term investments on the Company’s consolidated balance sheets as of December 31, 2014 and 2013 (in thousands):
		31-Dec-14
		Gross			Gross			Gross			Aggregated
		Amortized			Unrealized			Unrealized			Estimated
		Costs			Gains			Losses			Fair Value
	U.S. Government and agency securities including	$	1,009,827		$	8		$	(294	)	$	1,009,541
	treasury bills
	Corporate notes, certificates of deposit and		1,102,275			4			(666	)		1,101,613
	commercial paper
	Total available-for-sale securities classified as	$	2,112,102		$	12		$	(960	)	$	2,111,154
	short-term investments
		31-Dec-13
		Gross			Gross			Gross			Aggregated
		Amortized			Unrealized			Unrealized			Estimated
		Costs			Gains			Losses			Fair Value
	U.S. Government and agency securities including	$	785,535		$	22		$	(21	)	$	785,536
	treasury bills
	Corporate notes, certificates of deposit and		607,590			11			(93	)		607,508
	commercial paper
	Total available-for-sale securities classified as	$	1,393,125		$	33		$	(114	)	$	1,393,044
	short-term investments
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	The following tables show all short-term investments in an unrealized loss position for which other-than-temporary impairment has not been recognized and the related gross unrealized losses and fair value, aggregated by investment category and the length of time that individual securities have been in a continuous unrealized loss position (in thousands):
		31-Dec-14
		Less than 12 Months						12 Months or Greater					Total
					Unrealized						Unrealized				Unrealized
		Fair Value			Loss			Fair Value			Loss		Fair Value		Loss
	U.S. Government and agency securities	$	766,997		$	(294	)	$	—		$	—	$	766,997	$	(294	)
	including treasury bills
	Corporate notes, certificates of deposit		525,097			(666	)		—			—		525,097		(666	)
	and commercial paper
	Total short-term investments in an	$	1,292,094		$	(960	)	$	—		$	—	$	1,292,094	$	(960	)
	unrealized loss position
		31-Dec-13
		Less than 12 Months						12 Months or Greater					Total
					Unrealized						Unrealized				Unrealized
		Fair Value			Loss			Fair Value			Loss		Fair Value		Loss
	U.S. Government and agency securities	$	230,478		$	(21	)	$	—		$	—	$	230,478	$	(21	)
	including treasury bills
	Corporate notes, certificates of deposit		171,894			(93	)		—			—		171,894		(93	)
	and commercial paper
	Total short-term investments in an	$	402,372		$	(114	)	$	—		$	—	$	402,372	$	(114	)
	unrealized loss position

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2014 and 2013 based on the three-tier fair value hierarchy (in thousands):
		31-Dec-14
		Level 1		Level 2		Level 3		Total
	Assets
	Cash equivalents:
	Money market funds	$	882,443	$	—	$	—	$	882,443
	Treasury bills		73,525		—		—		73,525
	U.S. government securities		—		157,895		—		157,895
	Agency securities		—		39,998		—		39,998
	Corporate notes		—		13,684		—		13,684
	Commercial paper		—		185,321		—		185,321
	Certificates of deposit		—		10,010		—		10,010
	Short-term investments:
	Treasury bills		167,575		—		—		167,575
	U.S. government securities		—		746,128		—		746,128
	Agency securities		—		95,838		—		95,838
	Corporate notes		—		551,604		—		551,604
	Commercial paper		—		300,589		—		300,589
	Certificates of deposit		—		249,420		—		249,420
	Total	$	1,123,543	$	2,350,487	$	—	$	3,474,030
		31-Dec-13
		Level 1		Level 2		Level 3		Total
	Assets
	Cash equivalents:
	Money market funds	$	229,529	$	—	$	—	$	229,529
	Treasury bills		244,048		—		—		244,048
	U.S. government securities		—		7,545		—		7,545
	Corporate notes		—		1,011		—		1,011
	Commercial paper		—		194,742		—		194,742
	Short-term investments:
	Treasury bills		265,878		—		—		265,878
	U.S. government securities		—		501,372		—		501,372
	Agency securities		—		18,286		—		18,286
	Corporate notes		—		255,546		—		255,546
	Commercial paper		—		272,617		—		272,617
	Certificates of deposit		—		79,345		—		79,345
	Total	$	739,455	$	1,330,464	$	—	$	2,069,919

Property_and_Equipment_Net_Tab

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2014
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	The following table presents the detail of property and equipment, net for the periods presented (in thousands):
		December 31,			December 31,
		2014			2013
	Property and equipment, net
	Equipment	$	584,561		$	367,949
	Furniture and leasehold improvements		131,851			54,965
	Capitalized software		82,052			47,290
	Construction in progress		89,806			29,523
	Total		888,270			499,727
	Less: Accumulated depreciation and amortization		(331,251	)		(167,065	)
	Property and equipment, net	$	557,019		$	332,662

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Goodwill Activities	The following table presents the goodwill activities for the periods presented (in thousands):
	Goodwill
	Balance as of December 31, 2012	$	68,813
	Crashlytics acquisition		33,254
	Bluefin acquisition		60,019
	MoPub acquisition		192,446
	Other acquisitions		8,945
	Balance as of December 31, 2013	$	363,477
	Gnip acquisition		104,747
	Other acquisitions		155,054
	Foreign currency translation adjustment		(708	)
	Balance as of December 31, 2014	$	622,570
Schedule of Intangible Assets	The following table presents the detail of intangible assets for the periods presented (in thousands):
		Gross Carrying			Accumulated			Net Carrying
		Value			Amortization			Value
	December 31, 2014:
	Patents and developed technologies	$	105,052		$	(23,165	)	$	81,887
	Publisher and advertiser relationships		32,000			(9,831	)		22,169
	Assembled workforce		1,960			(1,457	)		503
	Other intangible assets		1,100			(648	)		452
	Total	$	140,112		$	(35,101	)	$	105,011
	December 31, 2013:
	Patents and developed technologies	$	100,553		$	(45,440	)	$	55,113
	Publisher and advertiser relationships		21,100			(1,248	)		19,852
	Assembled workforce		1,960			(300	)		1,660
	Other intangible assets		1,100			(98	)		1,002
	Total	$	124,713		$	(47,086	)	$	77,627
Schedule of Estimated Future Amortization Expenses	Estimated future amortization expense as of December 31, 2014 is as follows (in thousands):
	Years ending December 31,
	2015	$	35,446
	2016		26,260
	2017		11,624
	2018		9,832
	2019		5,430
	Thereafter		16,419
	Total	$	105,011

Other_Balance_Sheet_Components1

Other Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Prepaid and Other Current Assets	The following table presents the detail of prepaid and other current assets for the periods presented (in thousands):
		December 31,		December 31,
		2014		2013
	Deferred income tax assets, net	$	25,882	$	62,122
	Prepaid and other		189,639		31,175
	Total	$	215,521	$	93,297
Accrued and Other Current Liabilities	The following table presents the detail of accrued and other current liabilities for the periods presented (in thousands):
		December 31,		December 31,
		2014		2013
	Accrued compensation	$	68,000	$	29,882
	Accrued publisher payments		27,996		15,370
	Accrued sales and marketing expenses		25,264		1,813
	Deferred revenue		18,679		14,479
	Accrued tax liabilities		18,380		9,515
	Accrued professional services		13,543		7,089
	Accrued other		56,371		32,162
	Total	$	228,233	$	110,310

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2014
2013 Acquisitions
Summary of Unaudited Pro Forma Results of Operations	The following summary of unaudited pro forma results of operations of the Company for the years ended December 31, 2013 and 2012 is presented using the assumption that the business combinations made in 2013 were completed as of January 1, 2012. These pro forma results of the Company have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which would have resulted had the acquisitions occurred as of January 1, 2012, nor is it indicative of future operating results. The pro forma results presented include amortization charges for acquired intangible assets, adjustments for incremental compensation expense related to the post-combination service arrangements entered into with the continuing employees and related tax effects (in thousands):
		Year Ended December 31,
		2013			2012
		(Unaudited)
	Revenue	$	678,838		$	321,639
	Net loss		(667,404	)		(166,026	)
2012 Acquisitions
Summary of Unaudited Pro Forma Results of Operations	The following summary of unaudited pro forma results of operations of the Company for the years ended December 31, 2012 and 2011 is presented using the assumption that the acquisitions made in 2012 were completed as of January 1, 2011. These pro forma results of the Company have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which would have resulted had the acquisitions occurred as of January 1, 2011, nor is it indicative of future operating results. The pro forma results presented include amortization charges for acquired intangible assets, adjustments for incremental compensation expense related to the post-combination service arrangements entered into with the continuing employees and related tax effects (in thousands):
		Year Ended December 31,
		2012			2011
		(Unaudited)
	Revenue	$	316,933		$	106,313
	Net loss		(70,200	)		(166,317	)

Convertible_Notes_Tables

Convertible Notes (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Components of Notes	The Notes consisted of the following (in thousands):
		31-Dec-14
		2019 Notes			2021 Notes
	Principal amounts:
	Principal	$	935,000		$	954,000
	Unamortized initial purchasers' discount and debt discount (1)		(225,104	)		(287,876	)
	Net carrying amount	$	709,896		$	666,124
	Carrying amount of the equity component (2)	$	222,826		$	283,283

Net_Loss_Per_Share_Tables

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Basic and Diluted Net Loss Per Share	The following table presents the calculation of basic and diluted net loss per share for periods presented (in thousands, except per share data).
		Year Ended December 31,
		2014				2013				2012
	Net loss	$	(577,820	)		$	(645,323	)		$	(79,399	)
	Basic shares:
	Weighted-average common shares outstanding		613,944				196,675				120,845
	Weighted-average restricted stock		(8,954	)			(7,165	)			(3,444	)
	subject to repurchase
	Weighted-average shares used to compute		604,990				189,510				117,401
	basic net loss per share
	Diluted shares:
	Weighted-average shares used to compute		604,990				189,510				117,401
	diluted net loss per share
	Net loss per share attributable to common stockholders:
	Basic	$	(0.96	)		$	(3.41	)		$	(0.68	)
	Diluted	$	(0.96	)		$	(3.41	)		$	(0.68	)
Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders	The following number of potential common shares at the end of each period were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive for the periods presented (in thousands):
		Year Ended December 31,
		2014			2013				2012
	RSUs		64,135				95,723				42,526
	Warrants		24,329				117				117
	Stock options		20,420				42,246				48,787
	Shares subject to repurchase		8,051				10,986				4,237
	Employee stock purchase plan		1,284				1,896				—
	Since the Company expects to settle the principal amount of the outstanding Notes in cash, the Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable.  The conversion spread of 24.3 million shares will have a dilutive impact on diluted net income per share of common stock when the average market price of the Company’s common stock for a given period exceeds the conversion price of $77.64 per share for the Notes.
	If the average market price of the common stock exceeds the exercise price of the warrants, $105.28, the warrants will have a dilutive effect on the earnings per share assuming that the Company is profitable.  Since the average market price of the common stock is below $105.28, the warrants are anti-dilutive.

Common_Stock_and_Stockholders_1

Common Stock and Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Restricted Stock Activity	The activities for the restricted common stock issued to employees for the year ended December 31, 2014 are summarized as follows (in thousands, except per share data):
						Weighted-Average
			Number of			Grant-Date Fair
			Shares			Value Per Share
	Unvested restricted common stock at December 31, 2013			6,866		$	17.6
	Granted			2,468		$	33.8
	Vested			(3,956	)	$	17.68
	Canceled			(423	)	$	17.31
	Unvested restricted common stock at December 31, 2014			4,955		$	25.62
Summary of Stock Option Activity	A summary of stock option activity for the year ended December 31, 2014 is as follows (in thousands, except years and per share data):
			Options Outstanding
									Weighted-
						Weighted-			Average
						Average			Remaining
			Number of			Exercise			Contractual Life			Aggregate
			Shares			Price Per Share			(in years)			Intrinsic Value
	Outstanding at December 31, 2013			42,246		$	1.89			6.47		$	2,609,295
	Options granted			500		$	42.05
	Options assumed in connection with acquisitions			819		$	1.6
	Options exercised			(22,447	)	$	1.29
	Options canceled			(698	)	$	7.27
	Outstanding at December 31, 2014			20,420		$	3.33			5.78		$	667,538
	Vested and expected to vest at			20,097		$	3.18			5.75		$	659,695
	December 31, 2014 (1)
	Exercisable at December 31, 2014			17,295		$	1.65			5.44		$	591,755
	·	The expected to vest options are the result of applying pre-vesting forfeiture rate assumptions to unvested options outstanding.
Summary of RSU Activity	The following table summarizes the activity related to the Company’s Pre-2013 and Post-2013 RSUs for the year ended December 31, 2014.  For purposes of this table, vested RSUs represent the shares for which the service condition had been fulfilled as of each respective date (in thousands, except per share data):
			RSUs Outstanding
						Weighted-
						Average Grant-
						Date Fair Value
			Shares			Per Share
	Unvested and outstanding at December 31, 2013			79,876		$	19.54
	Granted			24,409		$	48.49
	Vested			(26,903	)	$	21.34
	Canceled			(13,247	)	$	23.02
	Unvested and outstanding at December 31, 2014			64,135		$	29.08
Compensation Expense Allocated	Stock-based compensation expense is allocated based on the cost center to which the award holder belongs. Total stock-based compensation expense by function for the years ended December 31, 2014, 2013 and 2012 is as follows (in thousands):
			Year Ended December 31,
			2014			2013			2012
	Cost of revenue		$	50,536		$	50,942		$	800
	Research and development			360,726			379,913			12,622
	Sales and marketing			157,263			114,440			1,346
	General and administrative			63,072			55,072			10,973
	Total		$	631,597		$	600,367		$	25,741
Employee Stock Options
Schedule of Share-based Payment Award, Valuation Assumptions	The weighted-average grant-date fair value of stock options granted to employees and assumed in connection with acquisitions in the years ended December 31, 2014, 2013 and 2012 was $30.12, $11.89 and $7.42 per share, respectively. The fair value of stock options granted to employees was determined using the Black-Scholes option pricing model with the following weighted-average assumptions:
			Year Ended December 31,
			2014			2013			2012
	Expected dividend yield			—			—			—
	Risk-free interest rate			1.47	%		1.24	%		1.3	%
	Expected volatility			42.54	%		52.14	%		51.79	%
	Expected term (in years)			4.73			5.37			6.56

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Summary of Domestic and Foreign Components of Pre-Tax Loss	The domestic and foreign components of pre-tax loss for the years ended December 31, 2014, 2013 and 2012 are as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Domestic	$	(164,854	)	$	(549,397	)	$	(53,699	)
	Foreign		(413,497	)		(97,749	)		(25,471	)
	Loss before income taxes	$	(578,351	)	$	(647,146	)	$	(79,170	)
Components of Provision (Benefit) for Income Taxes	The components of the provision (benefit) for income taxes for the years ended December 31, 2014, 2013 and 2012 are as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Current:
	Federal	$	—		$	—		$	—
	State		720			857			(300	)
	Foreign		8,358			6,222			1,627
	Total current provision for income taxes		9,078			7,079			1,327
	Deferred:
	Federal		(8,972	)		(5,412	)		(608	)
	State		(128	)		(453	)		(89	)
	Foreign		(509	)		(3,037	)		(401	)
	Total deferred benefit for income taxes		(9,609	)		(8,902	)		(1,098	)
	Provision (benefit) for income taxes	$	(531	)	$	(1,823	)	$	229
Schedule of Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate	The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate for the years ended December 31, 2014, 2013 and 2012:
		Year Ended December 31,
		2014			2013			2012
	Tax at federal statutory rate		35	%		35	%		35	%
	State taxes, net of federal benefit		(0.1	)		(0.1	)		0.5
	Stock-based compensation		(4.2	)		(2.9	)		(1.9	)
	Research and development credits		25.2			3.6			—
	Valuation Allowance		(9.4	)		(25.0	)		(10.1	)
	Nondeductible expenses		(4.5	)		(3.0	)		(8.7	)
	Foreign rate differential		(26.4	)		(5.8	)		(12.7	)
	Change in tax positions		(15.9	)		(2.0	)		(2.8	)
	Other		0.4			0.5			0.4
	Effective tax rate		0.1	%		0.3	%		(0.3	)%
Schedule of Tax Effects of Temporary Differences and Related Deferred Tax Assets and Liabilities	The tax effects of temporary differences and related deferred tax assets and liabilities as of December 31, 2014 and 2013 are as follows (in thousands):
		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carryforwards	$	230,417		$	82,719
	Accruals and reserves		20,496			11,435
	Stock-based compensation expense		89,159			195,338
	Research and development credits		168,934			28,572
	California Enterprise Zone Credit		10,355			8,163
	Other		3,145			1,131
	Total deferred tax assets		522,506			327,358
	Valuation allowance		(351,249	)		(227,878	)
	Total deferred tax assets, net of valuation allowance		171,257			99,480
	Deferred tax liabilities:
	Fixed assets and intangible assets		(132,671	)		(80,072	)
	Convertible notes		(35,133	)		—
	Other		(420	)		(457	)
	Total deferred tax liabilities		(168,224	)		(80,529	)
	Net deferred tax assets	$	3,033		$	18,951
Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefit	A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows (in thousands):
		Year Ended December 31,
		2014			2013			2012
	Balance at the beginning of the year	$	43,061		$	23,352		$	25,845
	Additions related to prior year tax positions		—			7,880			—
	Reductions related to prior year tax positions		(50	)		—			(3,612	)
	Additions related to current year tax positions		139,473			11,829			1,119
	Balance at the end of the year	$	182,484		$	43,061		$	23,352
Summary of Unrecognized Tax Benefits Recorded in Balance Sheet	Total unrecognized tax benefits are recorded on the Company’s consolidated balance sheets as follows (in thousands):
		December 31,
		2014			2013
	Total unrecognized tax benefits balance	$	182,484		$	43,061
	Amounts netted against related deferred tax assets		(181,786	)		(27,160	)
	Unrecognized tax benefits recorded on consolidated balance sheets	$	698		$	15,901

Commitment_and_Contingencies_T

Commitment and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Minimum Commitments Under Non-Cancelable Capital and Operating Lease Agreements	A summary of gross and net lease commitments as of December 31, 2014 is as follows (in thousands):
		Operating		Capital
		Leases		Leases
	Years ending December 31,
	2015	$	110,221	$	119,771
	2016		135,625		81,758
	2017		138,663		38,818
	2018		134,667		4,159
	2019		102,932		—
	Thereafter		296,371		—
		$	918,479		244,506
	Less: Amounts representing interest				13,236
	Total capital lease obligation				231,270
	Less: Short-term portion				112,320
	Long-term portion			$	118,950

Segment_Information_and_Operat1

Segment Information and Operations by Geographic Area (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Revenue by Geography	Revenue by geography is based on the billing addresses of the customers. The following tables set forth revenue by services and revenue by geographic area (in thousands):
		Year Ended December 31,
		2014		2013		2012
		(in thousands)
	Advertising services	$	1,255,688	$	594,546	$	269,421
	Data licensing and other		147,314		70,344		47,512
	Total Revenue	$	1,403,002	$	664,890	$	316,933
		Year Ended December 31,
		2014		2013		2012
	Revenue:
	United States	$	945,720	$	492,320	$	263,917
	International		457,282		172,570		53,016
	Total revenue	$	1,403,002	$	664,890	$	316,933
Property and Equipment Net by Geographic Area	The following table sets forth property and equipment, net by geographic area (in thousands):
		December 31,		December 31,
		2014		2013
	Property and equipment, net:
	United States	$	523,810	$	327,250
	International		33,209		5,412
	Total property and equipment, net	$	557,019	$	332,662

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Accounting Policies [Line Items]
Capital lease obligations included in short-term and long-term	$231,300,000	$197,600,000
Interest expense in relation to capital lease arrangements.	10,200,000	7,000,000	3,100,000
Long-term investments	0	0
Interest earned on investments in marketable securities	1,900,000	700,000	800,000
Impairment charges on goodwill	0
Impairment charges on intangible assets	0
Software developing program costs capitalized	79,500,000	35,600,000	11,600,000
Percent likelihood for tax benefit amounts to be realized upon settlement	50.00%
Advertising expense	46,600,000	3,100,000	700,000
Cost of Revenue
Significant Accounting Policies [Line Items]
Amortization of capitalized costs	15,200,000	6,700,000	5,600,000
Internal Use Software and Website Development Costs
Significant Accounting Policies [Line Items]
Share-based compensation, capitalized amount	40,800,000	13,600,000	1,300,000
Customer Concentration Risk | Accounts Receivable
Significant Accounting Policies [Line Items]
Percentage of customer accountability of credit losses	10.00%
Customer Concentration Risk | Revenue
Significant Accounting Policies [Line Items]
Percentage of customer accountability of credit losses	10.00%	10.00%	10.00%
Prepaid Expenses and Other Current Assets
Significant Accounting Policies [Line Items]
Restricted Cash Balances	2,600,000	4,900,000
Other assets
Significant Accounting Policies [Line Items]
Restricted Cash Balances	$28,300,000	$15,300,000
Minimum
Significant Accounting Policies [Line Items]
Capital leases term	2 years
Intangible assets, estimated useful lives	1 year
Minimum | Internal Use Software and Website Development Costs
Significant Accounting Policies [Line Items]
Estimated useful life	1 year
Maximum
Significant Accounting Policies [Line Items]
Capital leases term	4 years
Intangible assets, estimated useful lives	11 years
Maximum | Internal Use Software and Website Development Costs
Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Employee Stock Options
Significant Accounting Policies [Line Items]
Stock-based compensation expense, dividend yield	0.00%

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2014
Computer Hardware and Networking Equipment | Minimum
Property Plant And Equipment [Line Items]
Estimated useful life	2 years
Computer Hardware and Networking Equipment | Maximum
Property Plant And Equipment [Line Items]
Estimated useful life	4 years
Computer Software | Minimum
Property Plant And Equipment [Line Items]
Estimated useful life	1 year
Computer Software | Maximum
Property Plant And Equipment [Line Items]
Estimated useful life	3 years
Office Equipment and Other | Maximum
Property Plant And Equipment [Line Items]
Estimated useful life	5 years
Leased Equipment and Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated useful life	Lesser of estimated useful life or remaining lease term

Cash_Cash_Equivalents_and_Shor2

Cash, Cash Equivalents and Short-term Investments - Cash, Cash and Equivalents and Short-term Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Cash and cash equivalents:
Cash	$147,848	$164,135
Cash and cash equivalents	1,510,724	841,010	203,328	218,996
Short-term investments:
Short-term investments	2,111,154	1,393,044
Money Market Funds
Cash and cash equivalents:
Cash and cash equivalents	882,443	229,529
U.S. Government and Agency Securities Including Treasury Bills
Cash and cash equivalents:
Cash and cash equivalents	271,418	251,593
Short-term investments:
Short-term investments	1,009,541	785,536
Corporate Notes Certificates Of Deposit And Commercial Paper
Cash and cash equivalents:
Cash and cash equivalents	209,015	195,753
Short-term investments:
Short-term investments	$1,101,613	$607,508

Cash_Cash_Equivalents_and_Shor3

Cash, Cash Equivalents and Short-term Investments - Summary of Unrealized Gains and Losses Related to Available-for-Sale Securities Classified as Short-term Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Gross Amortized Costs	$2,112,102	$1,393,125
Gross Unrealized Gains	12	33
Gross Unrealized Losses	-960	-114
Short-term investments	2,111,154	1,393,044
U.S. Government and Agency Securities Including Treasury Bills
Schedule Of Available For Sale Securities [Line Items]
Gross Amortized Costs	1,009,827	785,535
Gross Unrealized Gains	8	22
Gross Unrealized Losses	-294	-21
Short-term investments	1,009,541	785,536
Corporate Notes Certificates Of Deposit And Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Gross Amortized Costs	1,102,275	607,590
Gross Unrealized Gains	4	11
Gross Unrealized Losses	-666	-93
Short-term investments	$1,101,613	$607,508

Cash_Cash_Equivalents_and_Shor4

Cash, Cash Equivalents and Short-term Investments - Summary of Short-term Investments in Unrealized Loss Position and Related Gross Unrealized Losses and Fair Value, Aggregated by Investment Category and Length of Time (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	$1,292,094	$402,372
Less than 12 Months, Unrealized Loss	-960	-114
Total Fair Value	1,292,094	402,372
Total Unrealized Loss	-960	-114
U.S. Government and Agency Securities Including Treasury Bills
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	766,997	230,478
Less than 12 Months, Unrealized Loss	-294	-21
Total Fair Value	766,997	230,478
Total Unrealized Loss	-294	-21
Corporate Notes, Certificates of Deposit and Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	525,097	171,894
Less than 12 Months, Unrealized Loss	-666	-93
Total Fair Value	525,097	171,894
Total Unrealized Loss	($666)	($93)

Cash_Cash_Equivalents_and_Shor5

Cash, Cash Equivalents and Short-term Investments - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]
Impairment loss on securities	$0	$0

Fair_Value_Measurements_Schedu

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) (Fair Value, Measurements, Recurring, USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets
Total	$3,474,030	$2,069,919
Agency Securities
Assets
Cash equivalents	39,998
Short-term investments	95,838	18,286
Money Market Funds
Assets
Cash equivalents	882,443	229,529
Treasury Bills
Assets
Cash equivalents	73,525	244,048
Short-term investments	167,575	265,878
US Government Securities
Assets
Cash equivalents	157,895	7,545
Short-term investments	746,128	501,372
Corporate Notes
Assets
Cash equivalents	13,684	1,011
Short-term investments	551,604	255,546
Commercial Paper
Assets
Cash equivalents	185,321	194,742
Short-term investments	300,589	272,617
Certificates of Deposit
Assets
Cash equivalents	10,010
Short-term investments	249,420	79,345
Level 1
Assets
Total	1,123,543	739,455
Level 1 | Money Market Funds
Assets
Cash equivalents	882,443	229,529
Level 1 | Treasury Bills
Assets
Cash equivalents	73,525	244,048
Short-term investments	167,575	265,878
Level 2
Assets
Total	2,350,487	1,330,464
Level 2 | Agency Securities
Assets
Cash equivalents	39,998
Short-term investments	95,838	18,286
Level 2 | US Government Securities
Assets
Cash equivalents	157,895	7,545
Short-term investments	746,128	501,372
Level 2 | Corporate Notes
Assets
Cash equivalents	13,684	1,011
Short-term investments	551,604	255,546
Level 2 | Commercial Paper
Assets
Cash equivalents	185,321	194,742
Short-term investments	300,589	272,617
Level 2 | Certificates of Deposit
Assets
Cash equivalents	10,010
Short-term investments	$249,420	$79,345

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Details) (Level 2, USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Convertible Senior Notes 2019
Fair Value Disclosure [Line Items]
Estimated fair value of notes based on a market approach	$817.50
Convertible Senior Notes 2021
Fair Value Disclosure [Line Items]
Estimated fair value of notes based on a market approach	$832.30

Property_and_Equipment_Net_Sch

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property and equipment, net
Property and equipment, gross	$888,270	$499,727
Less: Accumulated depreciation and amortization	-331,251	-167,065
Property and equipment, net	557,019	332,662
Equipment
Property and equipment, net
Property and equipment, gross	584,561	367,949
Furniture and Leasehold Improvements
Property and equipment, net
Property and equipment, gross	131,851	54,965
Computer Software
Property and equipment, net
Property and equipment, gross	82,052	47,290
Construction in Progress
Property and equipment, net
Property and equipment, gross	$89,806	$29,523

Property_and_Equipment_Net_Add

Property and Equipment, Net - Additional Information (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property Plant And Equipment [Line Items]
Depreciation expense	$171.60	$94.40	$53.80
Computer Hardware and Networking Equipment
Property Plant And Equipment [Line Items]
Gross carrying amount of property and equipment	411.3	283.8
Accumulated depreciation of the equipment	182.4	86.2
Depreciation expense	$108.70	$70.40	$40.50

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Schedule of Goodwill Activities (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Beginning balance	$363,477	$68,813
Foreign currency translation adjustment	-708
Ending balance	622,570	363,477
Crashlytics
Goodwill [Line Items]
Acquisition		33,254
Bluefin Labs Inc
Goodwill [Line Items]
Acquisition		60,019
Mo Pub Inc
Goodwill [Line Items]
Acquisition		192,446
Gnip Inc
Goodwill [Line Items]
Acquisition	104,747
Other acquisitions
Goodwill [Line Items]
Acquisition	$155,054	$8,945	$20,100

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Finite Lived Intangible Assets [Line Items]
Impairment charges on goodwill	$0
Amortization of intangible assets	36,600,000	16,500,000
Other indefinite-lived intangible assets	$48,500,000
Minimum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	1 year
Maximum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	11 years
Patents and Developed Technologies | Minimum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	1 year
Patents and Developed Technologies | Maximum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	11 years
Publisher and Advertiser Relationships | Minimum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	2 years
Publisher and Advertiser Relationships | Maximum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	3 years
Assembled Workforce and Other Intangible Assets | Minimum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	2 years
Assembled Workforce and Other Intangible Assets | Maximum
Finite Lived Intangible Assets [Line Items]
Intangible assets, estimated useful lives	4 years

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$140,112	$124,713
Accumulated Amortization	-35,101	-47,086
Net Carrying Value	105,011	77,627
Patents and Developed Technologies
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	105,052	100,553
Accumulated Amortization	-23,165	-45,440
Net Carrying Value	81,887	55,113
Publisher and Advertiser Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	32,000	21,100
Accumulated Amortization	-9,831	-1,248
Net Carrying Value	22,169	19,852
Assembled Workforce
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	1,960	1,960
Accumulated Amortization	-1,457	-300
Net Carrying Value	503	1,660
Other Intangible Assets
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	1,100	1,100
Accumulated Amortization	-648	-98
Net Carrying Value	$452	$1,002

Goodwill_and_Intangible_Assets5

Goodwill and Intangible Assets - Schedule of Estimated Future Amortization Expenses (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]
2015	$35,446
2016	26,260
2017	11,624
2018	9,832
2019	5,430
Thereafter	16,419
Net Carrying Value	$105,011	$77,627

Other_Balance_Sheet_Components2

Other Balance Sheet Components - Prepaid and Other Current Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Deferred income tax assets, net	$25,882	$62,122
Prepaid and other	189,639	31,175
Total	$215,521	$93,297

Other_Balance_Sheet_Components3

Other Balance Sheet Components - Accrued and Other Current Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]
Accrued compensation	$68,000	$29,882
Accrued publisher payments	27,996	15,370
Accrued sales and marketing expenses	25,264	1,813
Deferred revenue	18,679	14,479
Accrued tax liabilities	18,380	9,515
Accrued professional services	13,543	7,089
Accrued other	56,371	32,162
Total	$228,233	$110,310

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Details) (USD $)	12 Months Ended			1 Months Ended				0 Months Ended
Share data in Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-14	Jan. 31, 2013	Feb. 28, 2013	Oct. 31, 2013	Jan. 31, 2012
Business Acquisition [Line Items]
Fair value of contingent payment	$97,700,000	$83,100,000	$28,500,000
Equity compensation service period	4 years	48 months	48 months
Acquisition of intangible assets for total purchase price		38,500,000
Granted, options		2
Revenues		9,600,000	0
Loss		42,300,000	26,900,000
Fair value of contingently returned shares value		0
Class A Junior Preferred Stock
Business Acquisition [Line Items]
Fair value of contingently returnable shares value			4,000,000
Common Stock
Business Acquisition [Line Items]
Fair value of contingently returnable shares value			3,000,000
Minimum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	1 year
Maximum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	11 years
Developed Technology Rights
Business Acquisition [Line Items]
Acquisition of intangible assets for total purchase price		500,000
Publisher and Advertiser Relationships | Minimum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	2 years
Publisher and Advertiser Relationships | Maximum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	3 years
Patents
Business Acquisition [Line Items]
Acquisition of intangible assets for total purchase price		36,000,000
Assembled Workforce
Business Acquisition [Line Items]
Acquisition of intangible assets for total purchase price		2,000,000
Patents Developed Technology And Assembled Work Force | Minimum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives		1 year
Patents Developed Technology And Assembled Work Force | Maximum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives		11 years
Gnip Inc
Business Acquisition [Line Items]
Business acquisition, purchase price cash consideration				107,300,000
Business acquisition, common stock issued including shares of restricted stock				0.6
Business acquisition, common shares issuable in respect of assumed equity awards held by individuals				0.4
Business Combination, Consideration Transferred				134,100,000
Acquisition purchase price allocated to liability				5,800,000
Acquisition purchase price allocated to deferred tax liability				6,400,000
Goodwill acquired	104,747,000
Acquisition purchase price allocated to assets				9,100,000
Gnip Inc | Developed Technology Rights
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets				23,200,000
Intangible assets, estimated useful lives	60 months
Gnip Inc | Customer Relationships
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets				9,300,000
Intangible assets, estimated useful lives	60 months
Other acquisitions
Business Acquisition [Line Items]
Business acquisition, purchase price cash consideration	66,900,000	5,800,000	5,000,000
Business Combination, Consideration Transferred	188,100,000	13,200,000	33,100,000
Acquisition purchase price allocated to liability		200,000
Acquisition purchase price allocated to deferred tax liability	3,200,000
Goodwill acquired	155,054,000	8,945,000	20,100,000
Acquisition purchase price allocated to assets	6,500,000		4,700,000
Number of businesses acquired	8	5	9
Business acquisition, common stock issued	121,200,000	7,400,000
Business acquisition, goodwill expected tax deductible amount	21,900,000	7,300,000	10,000,000
Acquisition purchase price allocated to cash			3,500,000
Other acquisitions | Class A Junior Preferred Stock
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			28,100,000
Other acquisitions | Developed Technology Rights
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets	28,100,000	4,500,000	8,300,000
Intangible assets, estimated useful lives			12 months
Other acquisitions | Developed Technology Rights | Minimum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	12 months	24 months
Other acquisitions | Developed Technology Rights | Maximum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	48 months	36 months
Other acquisitions | Customer Relationships
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets	1,600,000
Other acquisitions | Customer Relationships | Minimum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	12 months
Other acquisitions | Customer Relationships | Maximum
Business Acquisition [Line Items]
Intangible assets, estimated useful lives	48 months
All Acquisitions | Employee Stock Options
Business Acquisition [Line Items]
Equity compensation service period	48 months	48 months
Unrecognized share-based compensation expense	16,900,000	24,500,000
Crashlytics
Business Acquisition [Line Items]
Business Combination, Consideration Transferred					38,200,000
Acquisition purchase price allocated to liability					100,000
Acquisition purchase price allocated to deferred tax liability					300,000
Goodwill acquired		33,254,000
Acquisition purchase price allocated to assets					300,000
Contingent consideration classified as equity, fair value disclosure					6,700,000
Crashlytics | Developed Technology Rights
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets					5,000,000
Intangible assets, estimated useful lives					12 months
Bluefin Labs Inc
Business Acquisition [Line Items]
Business Combination, Consideration Transferred						67,300,000
Acquisition purchase price allocated to liability						1,900,000
Goodwill acquired		60,019,000
Acquisition purchase price allocated to assets						1,800,000
Contingent consideration classified as equity, fair value disclosure						7,900,000
Bluefin Labs Inc | Developed Technology Rights
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets						7,400,000
Intangible assets, estimated useful lives						18 months
MoPubInc
Business Acquisition [Line Items]
Business acquisition, common stock issued including shares of restricted stock							11.2
Business Combination, Consideration Transferred							218,800,000
Acquisition purchase price allocated to deferred tax liability							5,500,000
Goodwill acquired		192,446,000
Acquired of the ownership interest percentage							100.00%
Unvested restricted stock							2
Receive aggregate stock option							1.2
Account receivables							22,100,000
Other tangible assets							1,200,000
Publisher payments liabilities							22,100,000
Other liabilities							4,400,000
Granted, options		1.2
MoPubInc | Developed Technology Rights
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets							12,900,000
Intangible assets, estimated useful lives							36 months
MoPubInc | Publisher and Advertiser Relationships
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets							21,100,000
Intangible assets, estimated useful lives							36 months
MoPubInc | Trade Name
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets							1,100,000
Intangible assets, estimated useful lives							24 months
Dasient Inc
Business Acquisition [Line Items]
Business acquisition, purchase price cash consideration								100,000
Business Combination, Consideration Transferred								19,100,000
Acquisition purchase price allocated to liability								1,400,000
Goodwill acquired								12,000,000
Acquisition purchase price allocated to assets								800,000
Acquired of the ownership interest percentage								100.00%
Dasient Inc | Class A Junior Preferred Stock
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned								19,000,000
Dasient Inc | Developed Technology Rights
Business Acquisition [Line Items]
Acquisition purchase price allocated to finite lived intangible assets								$7,700,000
Intangible assets, estimated useful lives								12 months

Acquisitions_Summary_of_Unaudi

Acquisitions - Summary of Unaudited Pro Forma Results of Operations (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
2013 Acquisitions
Business Acquisition [Line Items]
Revenue	$678,838	$321,639
Net loss	-667,404	-166,026
2012 Acquisitions
Business Acquisition [Line Items]
Revenue		316,933	106,313
Net loss		($70,200)	($166,317)

Convertible_Notes_Additional_I

Convertible Notes - Additional Information (Details) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended		1 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2014		Oct. 31, 2014
Debt Instrument [Line Items]
Initial purchasers' discount	$28,300,000	$28,300,000
Debt issuance costs		500,000
Proceeds from offerings, net of transaction costs	1,860,000
Debt Instrument, frequency of periodic payment			semi-annually
Debt Instrument, date of first required payment			15-Mar-15
Debt Instrument Payment Terms			The interest rates are fixed at 0.25% and 1.00% per annum and are payable semi-annually in arrears on March 15 and September 15 of each year, commencing on March 15, 2015.
Amortization of debt discount allocated to interest expense			1,400,000
Accrued coupon interest expense			3,300,000
Price percentage for repurchase of notes if repurchase option is elected			100.00%
Equity component of the convertible note issuance, net			100,000
Amortization of discount on convertible notes			18,823,000
Convertible notes			1,376,020,000
Number of shares authorized for repurchase under hedge agreement			24.3
Exercise price of the option to repurchase stock			$77.64
Purchases of convertible note hedges			407,169,000
Number of warrants issued			24.3
Exercise price of the warrants			$105
Proceeds from issuance of warrants			289,272,000
Interest Expense
Debt Instrument [Line Items]
Amortization of discount on convertible notes			18,800,000
Scenario One
Debt Instrument [Line Items]
Convertible debt instrument, consecutive trading days threshold			30 days
Convertible debt instrument, percentage of conversion price to trigger conversion to common stock			130.00%
Scenario One | Minimum
Debt Instrument [Line Items]
Convertible debt instrument, trading days threshold			20
Scenario Two
Debt Instrument [Line Items]
Convertible debt instrument, trading days threshold			5
Convertible debt instrument, consecutive trading days threshold			5 days
Convertible debt instrument, percentage of conversion price to trigger conversion to common stock			98.00%
Common Stock
Debt Instrument [Line Items]
Debt instrument, conversion principal amount			1,000
Debt Instrument, conversion ratio			12.8793
Conversion Price			$77.64
Debt Instrument, terms of conversion			Each $1,000 of principal of these notes will initially be convertible into 12.8793 shares of the Companybs common stock, which is equivalent to an initial conversion price of approximately $77.64 per share, subject to adjustment upon the occurrence of specified events.
Convertible Senior Notes Due At Two Thousand And Nineteen
Debt Instrument [Line Items]
Debt instrument, principal amount	900,000,000	900,000,000	935,000,000
Proceeds from Issuance of Debt					35,000,000
Initial purchasers' discount			225,104,000	[1]
Debt Instrument, conversion earliest date			15-Mar-19
Carrying amount of the equity component			222,826,000	[2]
Effective interest rate for amortization to interest expense			5.75%
Convertible notes			709,896,000
Remaining period for convertible debt			56 months
Convertible Senior Notes Due At Two Thousand Twenty One
Debt Instrument [Line Items]
Debt instrument, principal amount	900,000,000	900,000,000	954,000,000
Proceeds from Issuance of Debt					54,000,000
Initial purchasers' discount			287,876,000	[1]
Debt Instrument, conversion earliest date			15-Mar-21
Carrying amount of the equity component			283,283,000	[2]
Effective interest rate for amortization to interest expense			6.25%
Convertible notes			$666,124,000
Remaining period for convertible debt			80 months
[1]	Included in the consolidated balance sheets within convertible notes and amortized over the remaining lives of the Notes.
[2]	Included in the consolidated balance sheets within additional paid-in capital.

Convertible_Notes_Components_o

Convertible Notes - Components of Notes (Details) (USD $)	Dec. 31, 2014		Sep. 30, 2014
In Thousands, unless otherwise specified
Principal amounts:
Unamortized initial purchasers' discount and debt discount			($28,300)
Net carrying amount	1,376,020
Convertible Senior Notes Due At Two Thousand And Nineteen
Principal amounts:
Debt instrument, principal amount	935,000		900,000
Unamortized initial purchasers' discount and debt discount	-225,104	[1]
Net carrying amount	709,896
Carrying amount of the equity component	222,826	[2]
Convertible Senior Notes Due At Two Thousand Twenty One
Principal amounts:
Debt instrument, principal amount	954,000		900,000
Unamortized initial purchasers' discount and debt discount	-287,876	[1]
Net carrying amount	666,124
Carrying amount of the equity component	$283,283	[2]
[1]	Included in the consolidated balance sheets within convertible notes and amortized over the remaining lives of the Notes.
[2]	Included in the consolidated balance sheets within additional paid-in capital.

Net_Loss_Per_Share_Basic_and_D

Net Loss Per Share - Basic and Diluted Net Loss Per Share (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net loss	($577,820)	($645,323)	($79,399)
Basic shares:
Weighted-average common shares outstanding	613,944	196,675	120,845
Weighted-average restricted stock subject to repurchase	-8,954	-7,165	-3,444
Basic	604,990	189,510	117,401
Diluted shares:
Diluted	604,990	189,510	117,401
Net loss per share attributable to common stockholders:
Basic	($0.96)	($3.41)	($0.68)
Diluted	($0.96)	($3.41)	($0.68)

Net_Loss_Per_Share_Summary_of_

Net Loss Per Share - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
RSUs
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from the computation of diluted net income per share	64,135	95,723	42,526
Warrant
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from the computation of diluted net income per share	24,329	117	117
Stock Options
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from the computation of diluted net income per share	20,420	42,246	48,787
Shares Subject to Repurchase
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from the computation of diluted net income per share	8,051	10,986	4,237
Employee Stock Purchase Plans
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from the computation of diluted net income per share	1,284	1,896

Net_Loss_Per_Share_Additional_

Net Loss Per Share - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share Basic [Line Items]
Exercise price of the warrants	$105.28
Convertible Senior Notes Due 2019 and 2021
Earnings Per Share Basic [Line Items]
Conversion Price	$77.64
Conversion spread will have a dilutive impact on diluted net income per share of common stock	24,300,000

Preferred_Stock_Additional_Inf

Preferred Stock - Additional Information (Details)	0 Months Ended	12 Months Ended
	Nov. 13, 2013	Dec. 31, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Conversion of share issued	329,600,000
Convertible preferred stock terms of conversion		Each share of preferred stock was convertible to one share of common stock. Upon the closing of the Companybs initial public offering on November 13, 2013
Preferred stock, shares outstanding		0	0
Preferred stock, shares authorized		200,000,000	200,000,000
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	77,000,000
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	49,300,000
Series C Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	62,800,000
Series D Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	51,000,000
Series E Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	38,400,000
Series F Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	26,200,000
Series G Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding	24,900,000
Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of preferred stock to common stock, shares			-3,524,000
Redeemable Convertible Preferred Stock | Common Stock
Class Of Stock [Line Items]
Conversion of preferred stock to common stock, shares			3,524,000

Common_Stock_and_Stockholders_2

Common Stock and Stockholders' Equity (Deficit) - Additional Information (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 07, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized	5,000,000,000	5,000,000,000
Common stock, par value	$0.00	$0.00
Voting rights	Each share of common stock is entitled to one vote
Dividends declared	$0
Equity compensation service period	4 years	48 months	48 months
Compensation expense related to restricted stock	63,900,000	31,700,000	6,300,000
Options granted expire years	10 years
Income taxes paid	17,053,000	14,637,000
Stock option outstanding	20,420,000	42,246,000
Issuance of common stock upon purchases under employee stock purchase plan, shares	1,900,000
Employee stock purchase plan (ESOP), weighted average purchase price of shares purchased	$22.47
Stock options exercised, intrinsic value	872,800,000	123,700,000	84,600,000
Incremental Share-based compensation cost	32,600,000	0	0
Share-based compensation, weighted average grant date fair value	$30.12	$11.89	$7.42
Internal Use Software and Website Development Costs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, capitalized amount	40,800,000	13,600,000	1,300,000
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares initially reserved	68,300,000
Number of shares available for issuance	60,000,000
Outstanding shares of common stock percentage	5.00%
Stock options and restricted stock units outstanding	23,900,000
Common stock, reserved for future issuance	81,800,000
2007 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options and restricted stock units outstanding		59,100,000
Issuance of common stock upon initial public offering, shares	0
2013 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized stock-based compensation expense, weighted average recognition period	10 months 6 days
Number of shares available for issuance				11,300,000
Outstanding shares of common stock percentage				1.00%
Common stock, reserved for future issuance	15,800,000
Companybs common stock at a discount through payroll deductions				15.00%
Lower fair market value of common stock on the first trading day				85.00%
Share-based compensation expense	31,800,000	5,400,000
Unrecognized share-based compensation expense	15,400,000
Stock Options Assumed in Acquisition
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option outstanding	1,600,000
Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized stock-based compensation expense related to restricted stock	93,500,000
Unamortized stock-based compensation expense, weighted average recognition period	2 years 5 months 5 days
Restricted Common Stock | Minimum | All Acquisitions
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity compensation service period	2 years
Restricted Common Stock | Maximum | All Acquisitions
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity compensation service period	4 years
Pre-2013 RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized stock-based compensation expense related to restricted stock	48,600,000
Unamortized stock-based compensation expense, weighted average recognition period	1 year 9 months 15 days
Income taxes paid	17,100,000
Share-based compensation expense	84,400,000	433,500,000
Fair value of restricted stock units vested	888,100,000
Accumulated share based compensation		405,900,000
Share-based compensation recognized in subsequent period		27,600,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of restricted stock units vested	1,130,000,000
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized stock-based compensation expense, weighted average recognition period	2 years 3 months
Unamortized share-based compensation expense related to unvested stock options	33,300,000
Employee Stock Options | All Acquisitions
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity compensation service period	48 months	48 months
Unrecognized share-based compensation expense	16,900,000	24,500,000
Post-2013 RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized stock-based compensation expense related to restricted stock	$1,260,000,000
Unamortized stock-based compensation expense, weighted average recognition period	2 years 10 months 28 days

Common_Stock_and_Stockholders_3

Common Stock and Stockholders' Equity (Deficit) - Summary of Restricted Stock Activity (Details) (Restricted Common Stock, USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares, beginning of period	6,866
Number of Shares, granted	2,468
Number of Shares, vested	-3,956
Number of Shares, Canceled	-423
Number of Unvested Shares, end of period	4,955
Weighted Average Grant Date Fair Value Per Share, beginning of period	$17.60
Weighted Average Grant Date Fair Value Per Share, Granted	$33.80
Weighted Average Grant Date Fair Value Per Share, Vested	$17.68
Weighted Average Grant Date Fair Value Per Share, Canceled	$17.31
Weighted Average Grant Date Fair Value Per Share, end of period	$25.62

Common_Stock_and_Stockholders_4

Common Stock and Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Options Outstanding - Number of Shares
Outstanding at beginning of period	42,246
Options granted	500
Options assumed in connection with acquisitions	819
Options exercised	-22,447
Options canceled	-698
Outstanding at end of period	20,420	42,246
Vested and expected to vest at end of period	20,097
Exercisable at end of period	17,295
Options Outstanding - Weighted-Average Exercise Price Per Share
Outstanding at beginning of period	$1.89
Options granted	$42.05
Options assumed in connection with acquisitions	$1.60
Options exercised	$1.29
Options canceled	$7.27
Outstanding at end of period	$3.33	$1.89
Vested and expected to vest at end of period	$3.18
Exercisable at end of period	$1.65
Options Outstanding - Weighted-Average Remaining Contractual Life
Outstanding	5 years 9 months 11 days	6 years 5 months 19 days
Vested and expected to vest at end of period	5 years 9 months
Exercisable at end of period	5 years 5 months 9 days
Options Outstanding - Aggregate Intrinsic Value
Outstanding at beginning of period	$2,609,295
Outstanding at end of period	667,538	2,609,295
Vested and expected to vest at end of period	659,695
Exercisable at end of period	$591,755

Common_Stock_and_Stockholders_5

Common Stock and Stockholders' Equity (Deficit) - Summary of RSU Activity (Details) (RSUs, USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Unvested Shares, beginning of period	79,876
Number of Shares, granted	24,409
Number of Shares, vested	-26,903
Number of Shares, Canceled	-13,247
Number of Unvested Shares, end of period	64,135
Weighted Average Grant Date Fair Value Per Share, beginning of period	$19.54
Weighted Average Grant Date Fair Value Per Share, Granted	$48.49
Weighted Average Grant Date Fair Value Per Share, Vested	$21.34
Weighted Average Grant Date Fair Value Per Share, Canceled	$23.02
Weighted Average Grant Date Fair Value Per Share, end of period	$29.08

Common_Stock_and_Stockholders_6

Common Stock and Stockholders' Equity (Deficit) - Compensation Expense Allocated (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$631,597	$600,367	$25,741
Cost of Revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	50,536	50,942	800
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	360,726	379,913	12,622
Sales and Marketing
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	157,263	114,440	1,346
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$63,072	$55,072	$10,973

Common_Stock_and_Stockholders_7

Common Stock and Stockholders' Equity (Deficit) - Schedule of Share-based Payment Award, Valuation Assumptions (Details) (Employee Stock Options)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense, dividend yield	0.00%
Risk-free interest rate	1.47%	1.24%	1.30%
Expected volatility	42.54%	52.14%	51.79%
Expected term (in years)	4 years 8 months 23 days	5 years 4 months 13 days	6 years 6 months 22 days

Income_Taxes_Summary_of_Domest

Income Taxes - Summary of Domestic and Foreign Components of Pre-Tax Loss (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Domestic	($164,854)	($549,397)	($53,699)
Foreign	-413,497	-97,749	-25,471
Loss before income taxes	($578,351)	($647,146)	($79,170)

Income_Taxes_Components_of_Pro

Income Taxes - Components of Provision (Benefit) for Income Taxes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
State	$720	$857	($300)
Foreign	8,358	6,222	1,627
Total current provision for income taxes	9,078	7,079	1,327
Deferred:
Federal	-8,972	-5,412	-608
State	-128	-453	-89
Foreign	-509	-3,037	-401
Total deferred benefit for income taxes	-9,609	-8,902	-1,098
Provision (benefit) for income taxes	($531)	($1,823)	$229

Income_Taxes_Schedule_of_Recon

Income Taxes - Schedule of Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Tax at federal statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	-0.10%	-0.10%	0.50%
Stock-based compensation	-4.20%	-2.90%	-1.90%
Research and development credits	25.20%	3.60%
Valuation Allowance	-9.40%	-25.00%	-10.10%
Nondeductible expenses	-4.50%	-3.00%	-8.70%
Foreign rate differential	-26.40%	-5.80%	-12.70%
Change in tax positions	-15.90%	-2.00%	-2.80%
Other	0.40%	0.50%	0.40%
Effective tax rate	0.10%	0.30%	-0.30%

Income_Taxes_Schedule_of_Tax_E

Income Taxes - Schedule of Tax Effects of Temporary Differences and Related Deferred Tax Assets and Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Net operating loss carryforwards	$230,417	$82,719
Accruals and reserves	20,496	11,435
Stock-based compensation expense	89,159	195,338
Research and development credits	168,934	28,572
California Enterprise Zone Credit	10,355	8,163
Other	3,145	1,131
Total deferred tax assets	522,506	327,358
Valuation allowance	-351,249	-227,878
Total deferred tax assets, net of valuation allowance	171,257	99,480
Deferred tax liabilities:
Fixed assets and intangible assets	-132,671	-80,072
Convertible notes	-35,133
Other	-420	-457
Total deferred tax liabilities	-168,224	-80,529
Net deferred tax assets	$3,033	$18,951

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Contingency [Line Items]
Deferred tax assets	$3,033,000	$18,951,000
Undistributed earnings for foreign subsidiaries	42,900,000
Operating loss carryforwards related to excess tax benefit from stock-based compensation	2,490,000,000
Unrecognized tax benefits	182,484,000	43,061,000	23,352,000	25,845,000
Net unrecognized tax benefit included in the deferred and other long-term tax liabilities	698,000	15,901,000
Decrease in net deferred tax assets and the related liability for unrecognized tax benefits	15,800,000
California Enterprise Zone
Income Tax Contingency [Line Items]
Credit carryforwards amount	15,900,000
Credit carryforward, expiration year	2023
Uncertain Tax Positions
Income Tax Contingency [Line Items]
Significant accrued interest and penalties related to uncertain tax positions	0
Foreign Jurisdictions
Income Tax Contingency [Line Items]
Deferred tax assets	3,200,000
Federal
Income Tax Contingency [Line Items]
Net operating loss carryforwards	2,600,000,000
Operating loss carryforwards, expiration year	2027
Credit carryforward, expiration start year	2027
Federal | Research
Income Tax Contingency [Line Items]
Credit carryforwards amount	175,900,000
State
Income Tax Contingency [Line Items]
Net operating loss carryforwards	1,000,000,000
Operating loss carryforwards, expiration year	2015
State | Research
Income Tax Contingency [Line Items]
Credit carryforwards amount	$142,000,000

Income_Taxes_Schedule_of_Recon1

Income Taxes - Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefit (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Balance at the beginning of the year	$43,061	$23,352	$25,845
Additions related to prior year tax positions		7,880
Reductions related to prior year tax positions	-50		-3,612
Additions related to current year tax positions	139,473	11,829	1,119
Balance at the end of the year	$182,484	$43,061	$23,352

Income_Taxes_Summary_of_Remain

Income Taxes - Summary of Remaining Balances Recorded in Balance Sheets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Income Tax Uncertainties [Abstract]
Total unrecognized tax benefits balance	$182,484	$43,061	$23,352	$25,845
Amounts netted against related deferred tax assets	-181,786	-27,160
Unrecognized tax benefits recorded on consolidated balance sheets	$698	$15,901

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Commitments [Line Items]
Unsecured revolving credit facility	$1,000,000,000
Line of credit facility, expiration date	22-Oct-18
Line of credit facility, interest rate description	Loans under the credit facility bear interest, at the Companybs option, at (i) a base rate based on the highest of the prime rate, the federal funds rate plus 0.50% and an adjusted LIBOR rate for a one-month interest period plus 1.00%, in each case plus a margin ranging from 0.00% to 0.75% or (ii) an adjusted LIBOR rate plus a margin ranging from 1.00% to 1.75%.
Amended revolving credit agreement, leverage ratio above which security will be requited	2.50%
Amended revolving credit agreement, outstanding amount above which security will be requited	500,000,000
Amended revolving credit agreement, percentage of borrowed amount to borrowing capacity above which security will be requited	50.00%
Expiration year of operating lease, earliest	2015
Expiration year of operating lease, last	2026
Space lease and various lease amendments	2026
Total remaining lease commitment	233,300,000
Lease amendment	In addition, in 2014 the Company entered into a lease agreement for an additional data center facility and lease amendments for capacity expansion of existing data center facilities through 2023 and increased the total commitments to $464.5 million as of December 31, 2014
Total commitments		464,500,000
Operating leases, rent expense, net	73,900,000	35,400,000	19,400,000
Non-cancelable commitments	$38,900,000
Minimum
Other Commitments [Line Items]
Commitments due period	1 year
Maximum
Other Commitments [Line Items]
Commitments due period	2 years
Base Rate | Minimum
Other Commitments [Line Items]
Line of credit facility, interest rate	0.00%
Base Rate | Maximum
Other Commitments [Line Items]
Line of credit facility, interest rate	0.75%
London Interbank Offered Rate (LIBOR) | Minimum
Other Commitments [Line Items]
Line of credit facility, interest rate	1.00%
London Interbank Offered Rate (LIBOR) | Maximum
Other Commitments [Line Items]
Line of credit facility, interest rate	1.75%
Federal Funds Rate Plus 0.50%
Other Commitments [Line Items]
Line of credit facility, interest rate	0.50%
Libor Rate One Month Interest Period Plus 1.00%
Other Commitments [Line Items]
Line of credit facility, interest rate	1.00%

Commitments_and_Contingencies_1

Commitments and Contingencies - Minimum Commitments Under Non-Cancelable Capital and Operating Lease Agreements (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Capital Leases Future Minimum Payments Due [Abstract]
2015	$119,771
2016	81,758
2017	38,818
2018	4,159
2019	0
Thereafter	0
Total	244,506
Less: Amounts representing interest	13,236
Total capital lease obligation	231,270
Less: Short-term portion	112,320	87,126
Long-term portion	118,950	110,520
Operating Leases Future Minimum Payments Due [Abstract]
2015	110,221
2016	135,625
2017	138,663
2018	134,667
2019	102,932
Thereafter	296,371
Total	$918,479

Related_Party_Transactions_Add

Related Party Transactions - Additional Infomation (Details) (Director, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Director
Related Party Transaction [Line Items]
Related party transaction expense	$0	$0	$1,900,000
Due to related parties	$0

Segment_Information_and_Operat2

Segment Information and Operations by Geographic Area - Revenue by Geographic Area (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Revenue	$1,403,002	$664,890	$316,933
United States
Revenue:
Revenue	945,720	492,320	263,917
International
Revenue:
Revenue	457,282	172,570	53,016
Advertising Services
Revenue:
Revenue	1,255,688	594,546	269,421
Data Licensing And Other
Revenue:
Revenue	$147,314	$70,344	$47,512

Segment_Information_and_Operat3

Segment Information and Operations by Geographic Area - Additional Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$1,403,002	$664,890	$316,933
International
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	457,282	172,570	53,016
Revenue | United Kingdom
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$140,300	$66,500
Revenue | International
Revenues From External Customers And Long Lived Assets [Line Items]
Number of individual country that contributed in excess of ten percent to revenue			0
Geographic Concentration Risk | Revenue | United Kingdom
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue percentage	10.00%	10.00%

Segment_Information_and_Operat4

Segment Information and Operations by Geographic Area - Property and Equipment Net by Geographic Area (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property and equipment, net:
Property and equipment, net	$557,019	$332,662
United States
Property and equipment, net:
Property and equipment, net	523,810	327,250
International
Property and equipment, net:
Property and equipment, net	$33,209	$5,412

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Deferred Tax Assets
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$227,878	$42,175	$24,895
Charged to Expenses	155,111	180,691	15,250
Charged/Credited to Other Accounts	-31,740	5,012	2,030
Balance at End of Year	351,249	227,878	42,175
Allowance for Doubtful Accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	2,020	1,280	1,828
Additions (Reductions)	4,632	1,557	1,844
Write-off/ Adjustments	-1,145	-817	-2,392
Balance at End of Year	$5,507	$2,020	$1,280