Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Convertible Senior Notes 2019	Convertible Senior Notes Due 2022	Convertible Senior Notes 2025	Common Stock	Additional Paid-In Capital	Additional Paid-In Capital Convertible Senior Notes 2019	Additional Paid-In Capital Convertible Senior Notes Due 2022	Additional Paid-In Capital Convertible Senior Notes 2025	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2018						41,223
Beginning balance at Dec. 31, 2018	$ 321,226					$ 41	$ 709,691				$ (388,226)		$ (280)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)						425
Exercise of stock options	8,469					$ 1	8,468
Vested restricted stock units (in shares)						193
Common stock issued under employee stock (in shares)						67
Common stock issued under employee stock purchase plan	2,402						2,402
Stock-based compensation	33,650						33,650
Equity component of convertible debt			$ (233)					$ (233)
Other comprehensive loss (Note 13)	602												602
Net income (loss)	(11,016)										(11,016)
Ending balance (in shares) at Dec. 31, 2019						41,908
Ending balance at Dec. 31, 2019	$ 354,944	$ (156)				$ 42	753,978				(399,398)	$ (156)	322
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-02 [Member]
Exercise of stock options (in shares)						1,428
Exercise of stock options	$ 45,229					$ 2	45,227
Vested restricted stock units (in shares)						239
Common stock issued under employee stock (in shares)						62
Common stock issued under employee stock purchase plan	2,546						2,546
Stock-based compensation	39,920						39,920
Equity component of convertible debt				$ (33,089)	$ 64,619				$ (33,089)	$ 64,619
Other comprehensive loss (Note 13)	(4)												(4)
Net income (loss)	145,523										145,523
Ending balance (in shares) at Dec. 31, 2020						43,637
Ending balance at Dec. 31, 2020	619,688					$ 44	873,201				(253,875)		318
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)						732
Exercise of stock options	23,834					$ 1	23,833
Vested restricted stock units (in shares)						310
Common stock issued under employee stock (in shares)						55
Common stock issued under employee stock purchase plan	2,811						2,811
Stock-based compensation	42,246						42,246
Other comprehensive loss (Note 13)	(151)												(151)
Net income (loss)	41,980										41,980
Ending balance (in shares) at Dec. 31, 2021						44,734
Ending balance at Dec. 31, 2021	$ 730,408					$ 45	$ 942,091				$ (211,895)		$ 167