Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2018	38,325,037
Balance at Dec. 31, 2018	$ 4	$ 1,236,355	$ (12)	$ (1,202,041)	$ 34,306
Stock-based compensation	$ 0	57,327	0	0	57,327
Shares issued or restricted stock units vested under employee stock plans (in shares)	878,267
Shares issued or restricted stock units vested under employee stock plans	$ 0	1,351	0	0	1,351
Reclassifications of gain on available-for-sale securities, included in “Other income (expenses)," net of tax of $0, $0, and $0	0	0	2	0	2
Unrealized (loss) gain on available-for-sale securities, net of tax of $0, $0, and $0	0	0	72	0	72
Net loss	$ 0	0	0	(75,595)	(75,595)
Balance (in shares) at Dec. 31, 2019	39,203,304
Balance at Dec. 31, 2019	$ 4	1,295,033	62	(1,277,636)	17,463
Stock-based compensation	$ 0	36,575	0	0	36,575
Shares issued or restricted stock units vested under employee stock plans (in shares)	883,083
Shares issued or restricted stock units vested under employee stock plans	$ 0	68	0	0	68
Reclassifications of gain on available-for-sale securities, included in “Other income (expenses)," net of tax of $0, $0, and $0	0	0	3	0	3
Unrealized (loss) gain on available-for-sale securities, net of tax of $0, $0, and $0	0	0	(65)	0	(65)
Net loss	$ 0	0	0	(59,995)	$ (59,995)
Balance (in shares) at Dec. 31, 2020	40,086,387				40,086,387
Balance at Dec. 31, 2020	$ 4	1,331,676	0	(1,337,631)	$ (5,951)
Stock-based compensation	$ 0	32,633	0	0	32,633
Shares issued or restricted stock units vested under employee stock plans (in shares)	1,089,120
Shares issued or restricted stock units vested under employee stock plans	$ 0	0	0	0	0
Reclassifications of gain on available-for-sale securities, included in “Other income (expenses)," net of tax of $0, $0, and $0					0
Unrealized (loss) gain on available-for-sale securities, net of tax of $0, $0, and $0	0	0	(2)	0	(2)
Net loss	$ 0	0	0	(29,126)	$ (29,126)
Balance (in shares) at Dec. 31, 2021	41,175,507				40,086,387
Balance at Dec. 31, 2021	$ 4	$ 1,364,309	$ (2)	$ (1,366,757)	$ (2,446)