CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net	Total
Balance, beginning at Dec. 31, 2016	$ 16	$ (232)	$ 198,787	$ (199,536)	$ (1)
Balance, beginning (in shares) at Dec. 31, 2016	16,079,902	(18,906)
Increase (Decrease) in Stockholders Equity
Issuance of common stock, net of issuance costs	$ 12		64,548
Issuance of common stock, net of issuance costs (in shares)	12,019,639
Shares issued for exercise of stock options (in shares)	1,249
Purchase of treasury stock		$ (120)
Purchase of treasury stock (in shares)		(14,895)
Recognition of beneficial conversion feature on convertible notes			613			$ 613
Share-based compensation expense			4,051
Conversion of Redeemable Preferred Stock	$ 1		6,585
Issuance of common stock upon conversion of convertible notes (in shares)	929,967
Net unrealized gain (loss) on investments					(5)	(5)
Net loss				(65,772)		(65,772)
Balance, ending at Dec. 31, 2017	$ 29	$ (352)	274,584	(265,308)	(6)	8,947
Balance, ending (in shares) at Dec. 31, 2017	29,030,757	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock, net of issuance costs	$ 21		47,271
Issuance of common stock, net of issuance costs (in shares)	20,651,524
Issuance of common stock upon RSU conversion	26,991
Shares issued for exercise of stock options (in shares)	832
Payroll tax withheld for RSU releases			(46)
Share-based compensation expense			3,321
Net unrealized gain (loss) on investments					6	6
Net loss				(51,675)		(51,675)
Balance, ending at Dec. 31, 2018	$ 50	$ (352)	325,130	(316,983)		$ 7,845
Balance, ending (in shares) at Dec. 31, 2018	49,710,104	(33,801)				49,710,104
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	20,328
Shares issued for exercise of stock options			11
Shares issued for exercise of stock options (in shares)	36,040
Payroll tax withheld for RSU releases			(2)
Share-based compensation expense			2,917
Net unrealized gain (loss) on investments					1	$ 1
Net loss				(16,902)		(16,902)
Balance, ending at Dec. 31, 2019	$ 50	$ (352)	$ 328,056	$ (333,885)	$ 1	$ (6,130)
Balance, ending (in shares) at Dec. 31, 2019	49,766,472	(33,801)				49,766,472