Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Comprehensive (Loss) Income [Member]	Noncontrolling Interest in JV [Member]
Balance (in shares) at Dec. 31, 2014		67,667,000	2,193,000
Balance at Dec. 31, 2014	$ 920,091	$ 68	$ (50,000)	$ 1,045,078	$ (77,109)	$ 2,528	$ (474)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchase (in shares)	2,989,324	2,989,000
Employee stock purchases	$ 65,238	$ 3		65,235
Issuance of restricted stock awards (in shares)	166,042	166,000
Issuance of restricted stock awards	$ 0
Issuance of common stock (in shares)		945,000
Issuance of common stock	29,964	$ 1		29,963
Non-cash stock compensation	30,605			30,605
Equity component of the convertible notes issuance, net	37,177			37,177
Net loss	(352,746)				(352,756)		10
Currency translation adjustment	1,445					1,445
Amounts reclassified from accumulated other comprehensive income	0
Balance (in shares) at Dec. 31, 2015		71,767,000	2,193,000
Balance at Dec. 31, 2015	$ 731,774	$ 72	$ (50,000)	1,208,058	(429,865)	3,973	(464)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchase (in shares)	1,312,812	1,313,000
Employee stock purchases	$ 33,776	$ 1		33,775
Issuance of restricted stock awards (in shares)	132,344	132,000
Issuance of restricted stock awards	$ 0
Non-cash stock compensation	30,987			30,987
Reclassification from mezzanine equity	16,056			16,056
Equity component of 2017 Notes repurchased	(108,725)			(108,725)
Purchase of capped call transactions	(33,931)			(33,931)
Equity component of the convertible notes issuance, net	98,085			98,085
Settlement of hedges	(87,874)			(87,874)
Settlement of warrants	100,459			100,459
Net loss	(119,172)				(119,118)		(54)
Currency translation adjustment	213					213
Amounts reclassified from accumulated other comprehensive income	(9,665)					(9,665)
Balance (in shares) at Dec. 31, 2016		73,212,000	2,193,000
Balance at Dec. 31, 2016	$ 651,983	$ 73	$ (50,000)	1,256,890	(548,983)	(5,479)	(518)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchase (in shares)	1,949,117	1,949,000
Employee stock purchases	$ 48,621	$ 2		48,619
Purchase of shares from non-controlling interest	$ (167)			(685)			518
Issuance of restricted stock awards (in shares)	166,103	166,000
Issuance of restricted stock awards	$ 0
Non-cash stock compensation	31,520			31,520
Equity component of 2017 Notes repurchased	3			3
Equity component of the convertible notes issuance, net	1,031			1,031
Settlement of 2017 Notes (in shares)		(820,000)
Settlement of 2017 Notes	1	$ 1
Settlement of hedges (in shares)			(820,000)
Settlement of hedges	(1)		$ (40,016)	40,015
Settlement of warrants (in shares)		44,000
Settlement of warrants	0
Net loss	(708,373)				(708,373)
Currency translation adjustment	296					296
Amounts reclassified from accumulated other comprehensive income	0
Balance (in shares) at Dec. 31, 2017		76,191,000	3,013,000
Balance at Dec. 31, 2017	$ 24,914	$ 76	$ (90,016)	$ 1,377,393	$ (1,257,356)	$ (5,183)	$ 0