CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Company Stock Held By NQDC	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2013	$ 1,341,041	$ 144	$ 2,059,101	$ (7,421)	$ 5,018	$ (715,801)
Beginning Balance (in shares) at Dec. 31, 2013		143,464
Net loss	(133,969)					(133,969)
Other comprehensive income (loss)	22,448				22,448
Issuance of common stock, net of offering costs	117,464	$ 1	117,463
Issuance of common stock, net of offering costs (in shares)		1,500
Issuance of common stock under ESPP	8,714		8,714
Issuance of common stock under ESPP (in shares)		258
Issuances under equity incentive plans, net of tax	63,422	$ 3	63,419
Issuances under equity incentive plans, net of tax (in share)		2,817
Conversion of convertible notes, net (in shares)		1,055
Conversion of convertible notes, net	21,324	$ 1	21,323
Company stock held by NQDC	(2,274)			(2,274)
Excess tax benefit from stock option exercises	1,491		1,491
Stock-based compensation	88,233		88,233
Ending Balance at Dec. 31, 2014	1,527,894	$ 149	2,359,744	(9,695)	27,466	(849,770)
Ending Balance (in shares) at Dec. 31, 2014		149,094
Net loss	(171,799)					(171,799)
Other comprehensive income (loss)	(6,433)				(6,433)
Issuance of common stock, net of offering costs	888,257	$ 10	888,247
Issuance of common stock, net of offering costs (in shares)		9,775
Issuance of common stock under ESPP	9,957		9,957
Issuance of common stock under ESPP (in shares)		185
Issuances under equity incentive plans, net of tax	30,099	$ 2	30,097
Issuances under equity incentive plans, net of tax (in share)		2,023
Conversion of convertible notes, net (in shares)		449
Conversion of convertible notes, net	9,112	$ 1	9,111
Company stock held by NQDC	(3,921)			(3,921)
Excess tax benefit from stock option exercises	2,190		2,190
Stock-based compensation	115,491		115,491
Ending Balance at Dec. 31, 2015	2,400,847	$ 162	3,414,837	(13,616)	21,033	(1,021,569)
Ending Balance (in shares) at Dec. 31, 2015		161,526
Net loss	(630,210)					(630,210)
Cumulative Effect of New Accounting Principle in Period of Adoption	131,273					131,273
Other comprehensive income (loss)	(8,217)				(8,217)
Issuance of common stock, net of offering costs	712,938	$ 8	712,930
Issuance of common stock, net of offering costs (in shares)		7,500
Issuance of common stock under ESPP	11,998		11,998
Issuance of common stock under ESPP (in shares)		197
Issuances under equity incentive plans, net of tax	2,760	$ 3	2,757
Issuances under equity incentive plans, net of tax (in share)		2,987
Conversion of convertible notes, net (in shares)		438
Conversion of convertible notes, net	8,928		8,928
Company stock held by NQDC	(705)			(705)
Stock-based compensation	136,663		136,663
Ending Balance at Dec. 31, 2016	$ 2,766,275	$ 173	$ 4,288,113	$ (14,321)	$ 12,816	$ (1,520,506)
Ending Balance (in shares) at Dec. 31, 2016		172,648