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)			2,870
Exercise of options and restricted stock awards issued (in shares)			990
Issuance of common stock under employee purchase plan (in shares)			21
Ending Balance (in shares) at Jun. 30, 2021		0	61,489
Beginning Balance, amount at Dec. 31, 2020		$ 0	$ 58	$ 475,072		$ (492,966)		$ (45,067)	$ 91
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from issuance of common stock			2	22,120
Exercise of options			1	1,221
Issuance of common stock under employee purchase plan				161
Equity-based compensation				15,548
Net loss	$ (45,913)					(45,913)
Net unrealized loss on debt securities available-for-sale	(18)								(18)
Foreign currency translation adjustment	(60)								(60)
Ending Balance, amount at Jun. 30, 2021	(69,750)	$ 0	$ 61	514,122		(538,879)		(45,067)	13
Beginning Balance (in shares) at Mar. 31, 2021		0	59,561
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)			1,481
Exercise of options and restricted stock awards issued (in shares)			436
Issuance of common stock under employee purchase plan (in shares)			11
Ending Balance (in shares) at Jun. 30, 2021		0	61,489
Beginning Balance, amount at Mar. 31, 2021		$ 0	$ 60	495,857		(517,205)		(45,067)	(9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from issuance of common stock			1	11,455
Exercise of options				113
Issuance of common stock under employee purchase plan				81
Equity-based compensation				6,616
Net loss	(21,674)					(21,674)
Net unrealized loss on debt securities available-for-sale	1								1
Foreign currency translation adjustment	21								21
Ending Balance, amount at Jun. 30, 2021	(69,750)	$ 0	$ 61	514,122		(538,879)		(45,067)	13
Beginning Balance (in shares) at Dec. 31, 2021		3,955	67,649
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options and restricted stock awards issued (in shares)			1,128
Issuance of common stock under employee purchase plan (in shares)			125
Issuance of shares to retire Convertible Senior Notes (in shares)			10,799
Ending Balance (in shares) at Jun. 30, 2022		3,955	79,701
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]
Exercise of options			1	6
Issuance of shares to retire Convertible Notes			11	10,169
Issuance of common stock under employee purchase plan				137
Equity-based compensation				6,659
Net loss	(31,988)					(31,988)
Net unrealized loss on debt securities available-for-sale	(132)								(132)
Foreign currency translation adjustment	(240)								(240)
Ending Balance, amount at Jun. 30, 2022	(61,964)	$ 4	$ 80	560,185		(576,734)		(45,067)	(432)
Beginning Balance (in shares) at Mar. 31, 2022		3,955	68,712
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options and restricted stock awards issued (in shares)			974
Issuance of common stock under employee purchase plan (in shares)			66
Issuance of shares to retire Convertible Senior Notes (in shares)			9,949
Ending Balance (in shares) at Jun. 30, 2022		3,955	79,701
Beginning Balance, amount at Mar. 31, 2022		$ 4	$ 69	547,381		(558,211)		(45,067)	(232)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options			1	6
Issuance of shares to retire Convertible Notes			10	8,912
Issuance of common stock under employee purchase plan				60
Equity-based compensation				3,826
Net loss	(18,523)					(18,523)
Net unrealized loss on debt securities available-for-sale	(39)								(39)
Foreign currency translation adjustment	(161)								(161)
Ending Balance, amount at Jun. 30, 2022	$ (61,964)	$ 4	$ 80	$ 560,185		$ (576,734)		$ (45,067)	$ (432)