CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' DEFICIT Unaudited - USD ($) shares in Thousands, $ in Thousands	Total	Preferred stock shares outstanding	Common stock	Contributed capital	Contributed capital Cumulative effect of accounting changes	Accumulated deficit	Accumulated deficit Cumulative effect of accounting changes	Treasury stock	Accumulated other comprehensive (loss) income
Beginning Balance (in shares) at Dec. 31, 2020		0	57,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)			1,389
Exercise of options and restricted stock awards issued (in shares)			554
Issuance of common stock under employee purchase plan (in shares)			10
Issuance of shares to retire Convertible Senior Notes (in shares)			0
Ending Balance (in shares) at Mar. 31, 2021		0	59,561
Beginning Balance, amount at Dec. 31, 2020		$ 0	$ 58	$ 475,072	$ 0	$ (492,966)	$ 0	$ (45,067)	$ 91
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from issuance of common stock			1	10,665
Exercise of options			1	1,108
Issuance of shares to retire Convertible Notes			0	0
Issuance of common stock under employee purchase plan				80
Equity-based compensation				8,932
Net loss	$ (24,239)					(24,239)
Net unrealized loss on debt securities available-for-sale	(19)								(19)
Foreign currency translation adjustment	(81)								(81)
Ending Balance, amount at Mar. 31, 2021	(66,364)	$ 0	$ 60	495,857		(517,205)		(45,067)	(9)
Beginning Balance (in shares) at Dec. 31, 2021		3,955	67,649
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)			0
Exercise of options and restricted stock awards issued (in shares)			154
Issuance of common stock under employee purchase plan (in shares)			59
Issuance of shares to retire Convertible Senior Notes (in shares)			850
Ending Balance (in shares) at Mar. 31, 2022		3,955	68,712
Beginning Balance, amount at Dec. 31, 2021	(35,071)	$ 4	$ 68	580,652	$ (37,438)	(570,668)	$ 25,922	(45,067)	(60)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from issuance of common stock			0	0
Exercise of options			0	0
Issuance of shares to retire Convertible Notes			1	1,257
Issuance of common stock under employee purchase plan				77
Equity-based compensation				2,833
Net loss	(14,185)					(14,185)
Net unrealized loss on debt securities available-for-sale	(93)								(93)
Foreign currency translation adjustment	(79)								(79)
Ending Balance, amount at Mar. 31, 2022	$ (56,776)	$ 4	$ 69	$ 547,381		$ (558,931)		$ (45,067)	$ (232)