CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ DEFICIT - USD ($) $ in Thousands	Total	Common Shares	Preferred Shares	Cumulative impact of accounting change	Preferred Shares	Preferred Shares Preferred Shares	Common Shares	Common Shares Common Shares	Contributed Capital	Contributed Capital Common Shares	Contributed Capital Preferred Shares	Accumulated Deficit	Accumulated Deficit Cumulative impact of accounting change	Treasury stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance (shares) at Dec. 31, 2018					0		54,232,000
Beginning balance, amount at Dec. 31, 2018	$ 57,375				$ 0		$ 54		$ 432,885			$ (330,348)		$ (45,067)	$ (149)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(84,305)											(84,305)
Issuance of stock (shares)								56,000
Issuance of stock		$ 1,000								$ 1,000
Exercise of options and restricted stock awards issued (shares)							396,000
Exercise of options and restricted stock awards issued	5,365						$ 1		5,364
Issuance of common stock under employee purchase plan (shares)							25,000
Issuance of common stock under employee purchase plan	458								458
Unrealized gain on investments	193														193
Foreign currency translation adjustment	(102)														(102)
Equity-based compensation	12,637								12,637
Ending balance (shares) at Dec. 31, 2019					0		54,709,000
Ending balance, amount at Dec. 31, 2019	(7,379)			$ (105)	$ 0		$ 55		452,344			(414,653)	$ (105)	(45,067)	(58)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (78,208)											(78,208)
Exercise of options and restricted stock awards issued (shares)	2,631,935						2,858,000
Exercise of options and restricted stock awards issued	$ 6,062						$ 3		6,059
Issuance of common stock under employee purchase plan (shares)							41,000
Issuance of common stock under employee purchase plan	359								359
Unrealized gain on investments	(2)														(2)
Foreign currency translation adjustment	151														151
Equity-based compensation	16,310								16,310
Ending balance (shares) at Dec. 31, 2020					0		57,608,000
Ending balance, amount at Dec. 31, 2020	(62,812)				$ 0		$ 58		475,072			(492,966)		(45,067)	91
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(77,702)											(77,702)
Issuance of stock (shares)						3,955,000		4,937,000
Issuance of stock		$ 32,405	$ 30,450			$ 4		$ 5		$ 32,400	$ 30,446
Cancellation of common stock (shares)							(2,643,000)
Cancellation of common stock	$ (20,300)						$ (3)		(20,297)
Exercise of options and restricted stock awards issued (shares)	426,762						1,090,000
Exercise of options and restricted stock awards issued	$ 1,620						$ 1		1,619
Issuance of common stock under employee purchase plan (shares)							54,000
Issuance of common stock under employee purchase plan	326								326
Unrealized gain on investments	(34)														(34)
Foreign currency translation adjustment	(117)														(117)
Issuance of shares to retire Convertible Senior Notes (shares)							6,603,000
Issuance of shares to retire Convertible Senior Notes	38,903						$ 7		38,896
Equity-based compensation	22,190								22,190
Ending balance (shares) at Dec. 31, 2021					3,955,000		67,649,000
Ending balance, amount at Dec. 31, 2021	$ (35,071)				$ 4		$ 68		$ 580,652			$ (570,668)		$ (45,067)	$ (60)