Condensed Consolidated Statements of Stockholders' Equity (Unadited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest
Balance at beginning of year at Dec. 31, 2017	$ 349,493	$ 66	$ 1,551,728	$ (1,204,519)	$ (409)	$ 2,627
Balance at beginning of year (in shares) at Dec. 31, 2017		65,297
Adjustment to accumulated deficit due to adoption of ASC 606	29,037			29,037
Issuance of common stock pursuant to equity award plans	5,679	$ 1	5,678
Issuance of common stock pursuant to equity award plans (in shares)		514
Stock-based compensation expense	10,980		10,980
Other comprehensive income (loss)	(392)				(392)
Net income (loss)	(84,510)			(84,178)		(332)
Change in noncontrolling interest	(119)					(119)
Balance at end of the year at Mar. 31, 2018	310,168	$ 67	1,568,386	(1,259,660)	(801)	2,176
Balance at end of the year (in shares) at Mar. 31, 2018		65,811
Balance at beginning of year at Dec. 31, 2017	349,493	$ 66	1,551,728	(1,204,519)	(409)	2,627
Balance at beginning of year (in shares) at Dec. 31, 2017		65,297
Net income (loss)	(190,481)
Balance at end of the year at Jun. 30, 2018	220,061	$ 67	1,584,143	(1,365,854)	(674)	2,379
Balance at end of the year (in shares) at Jun. 30, 2018		65,954
Balance at beginning of year at Mar. 31, 2018	310,168	$ 67	1,568,386	(1,259,660)	(801)	2,176
Balance at beginning of year (in shares) at Mar. 31, 2018		65,811
Issuance of common stock pursuant to equity award plans	2,543		2,543
Issuance of common stock pursuant to equity award plans (in shares)		143
Stock-based compensation expense	13,214		13,214
Other comprehensive income (loss)	127				127
Net income (loss)	(105,971)			(106,194)		223
Change in noncontrolling interest	(20)					(20)
Balance at end of the year at Jun. 30, 2018	220,061	$ 67	1,584,143	(1,365,854)	(674)	2,379
Balance at end of the year (in shares) at Jun. 30, 2018		65,954
Balance at beginning of year at Dec. 31, 2018	90,567	$ 68	1,614,320	(1,525,704)	(283)	2,166
Balance at beginning of year (in shares) at Dec. 31, 2018		66,618
Issuance of common stock pursuant to equity award plans	25,662	$ 2	25,660
Issuance of common stock pursuant to equity award plans (in shares)		1,359
Stock-based compensation expense	12,312		12,312
Other comprehensive income (loss)	203				203
Net income (loss)	(78,096)			(78,156)		60
Change in noncontrolling interest	2					2
Balance at end of the year at Mar. 31, 2019	50,650	$ 70	1,652,292	(1,603,860)	(80)	2,228
Balance at end of the year (in shares) at Mar. 31, 2019		67,977
Balance at beginning of year at Dec. 31, 2018	90,567	$ 68	1,614,320	(1,525,704)	(283)	2,166
Balance at beginning of year (in shares) at Dec. 31, 2018		66,618
Net income (loss)	(146,573)
Foreign currency translation adjustment	(42)
Balance at end of the year at Jun. 30, 2019	594	$ 70	1,670,627	(1,670,064)	(39)
Balance at end of the year (in shares) at Jun. 30, 2019		68,235
Balance at beginning of year at Mar. 31, 2019	50,650	$ 70	1,652,292	(1,603,860)	(80)	2,228
Balance at beginning of year (in shares) at Mar. 31, 2019		67,977
Issuance of common stock pursuant to equity award plans	5,966		5,966
Issuance of common stock pursuant to equity award plans (in shares)		258
Stock-based compensation expense	12,369		12,369
Other comprehensive income (loss)	83				83
Net income (loss)	(68,477)			(66,204)		(2,273)
Change in noncontrolling interest	45					$ 45
Foreign currency translation adjustment	(42)				(42)
Balance at end of the year at Jun. 30, 2019	$ 594	$ 70	$ 1,670,627	$ (1,670,064)	$ (39)
Balance at end of the year (in shares) at Jun. 30, 2019		68,235