Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		49,422,991
Beginning balance at Dec. 31, 2018	$ 606,258	$ 5	$ 2,106,960	$ (155)	$ (1,500,552)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued from stock plans, net of payroll taxes paid (in shares)		747,962
Shares issued from stock plans, net of payroll taxes paid	13,147		13,147
Share-based compensation expense	53,047		53,047
Unrealized loss on available-for-sale investments	1,469			1,469
Translation gain (loss)	(11)			(11)
Net (loss) income	397,555				397,555
Ending balance (in shares) at Dec. 31, 2019		50,170,953
Ending balance at Dec. 31, 2019	1,071,465	$ 5	2,173,154	1,303	(1,102,997)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net (in shares)		6,325,000
Issuance of common stock, net	301,820	$ 1	301,819
Shares issued from stock plans, net of payroll taxes paid (in shares)		2,115,257
Shares issued from stock plans, net of payroll taxes paid	52,601		52,601
Share-based compensation expense	59,920		59,920
Unrealized loss on available-for-sale investments	(764)			(764)
Translation gain (loss)	161			161
Net (loss) income	$ (404,734)				(404,734)
Ending balance (in shares) at Dec. 31, 2020	58,611,210	58,611,210
Ending balance at Dec. 31, 2020	$ 1,080,469	$ 6	2,587,494	700	(1,507,731)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net (in shares)		1,241,142
Issuance of common stock, net	98,438		98,438
Shares issued from stock plans, net of payroll taxes paid (in shares)		1,711,770
Shares issued from stock plans, net of payroll taxes paid	41,370		41,370
Share-based compensation expense	70,373		70,373
Unrealized loss on available-for-sale investments	(1,168)			(1,168)
Translation gain (loss)	188			188
Net (loss) income	$ (616,433)				(616,433)
Ending balance (in shares) at Dec. 31, 2021	61,564,122	61,564,122
Ending balance at Dec. 31, 2021	$ 673,237	$ 6	$ 2,797,675	$ (280)	$ (2,124,164)