Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Contributed Capital	Accumulated Deficit	Treasury stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance (shares) at Dec. 31, 2016		51,516,000
Beginning balance, amount at Dec. 31, 2016	$ 77,816	$ 52	$ 255,257	$ (177,289)	$ 0	$ (204)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(64,028)			(64,028)
Issuance of common stock (shares)		3,085,000
Issuance of common stock	83,224	$ 3	83,221
Exercise of options, warrants and awards (shares)		1,045,000
Exercise of options, warrants and awards	6,606	$ 1	6,605
Issuance of common stock under employee purchase plan (shares)		28,000
Issuance of common stock under employee purchase plan	597		597
Unrealized loss on available-for-sale securities	(117)					(117)
Foreign currency translation adjustment	321					321
Equity-based compensation	14,940		14,940
Ending balance (shares) at Dec. 31, 2017		55,674,000
Ending balance, amount at Dec. 31, 2017	118,704	$ 56	360,620	(241,972)	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (88,326)			(88,326)
Exercise of options, warrants and awards (shares)	357,373	382,000
Exercise of options, warrants and awards	$ 3,749		3,749
Issuance of common stock under employee purchase plan (shares)		35,000
Issuance of common stock under employee purchase plan	583		583
Unrealized loss on available-for-sale securities	23					23
Foreign currency translation adjustment	(172)					(172)
Repurchase of common stock under Prepaid Forward contract (shares)		(1,859,000)
Repurchase of common stock under Prepaid Forward contract	(45,069)	$ (2)			(45,067)
Issuance of convertible note	53,283		53,283
Equity-based compensation	14,650		14,650
Ending balance (shares) at Dec. 31, 2018		54,232,000
Ending balance, amount at Dec. 31, 2018	57,375	$ 54	432,885	(330,348)	(45,067)	(149)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(84,305)			(84,305)
Issuance of common stock (shares)		56,000
Issuance of common stock	$ 1,000		1,000
Exercise of options, warrants and awards (shares)	383,319	396,000
Exercise of options, warrants and awards	$ 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 loss on available-for-sale securities	193					193
Foreign currency translation adjustment	$ (102)					(102)
Repurchase of common stock under Prepaid Forward contract (shares)	(1,858,500)
Equity-based compensation	$ 12,637		12,637
Ending balance (shares) at Dec. 31, 2019		54,709,000
Ending balance, amount at Dec. 31, 2019	$ (7,379)	$ 55	$ 452,344	$ (414,653)	$ (45,067)	$ (58)