CONDENSED 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, 2017	$ 29	$ (352)	$ 274,584	$ (265,308)	$ (6)
Balance, beginning (in shares) at Dec. 31, 2017	29,030,757	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock, net of issuance costs	$ 1		3,891
Issuance of common stock, net of issuance costs (in shares)	651,525
Issuance of common stock upon RSU conversion	25,429
Payroll tax withheld for RSU releases			(46)
Share-based compensation expense			2,902
Net unrealized gain (loss) on investments					6	$ 6
Net loss				(42,338)		(42,338)
Balance, ending at Sep. 30, 2018	$ 30	$ (352)	281,331	(307,646)		(26,637)
Balance, ending (in shares) at Sep. 30, 2018	29,707,711	(33,801)
Balance, beginning at Dec. 31, 2017	$ 29	$ (352)	274,584	(265,308)	(6)
Balance, beginning (in shares) at Dec. 31, 2017	29,030,757	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	26,991
Shares issued for exercise of stock options (in shares)	832
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)
Balance, beginning at Jun. 30, 2018	$ 29	$ (352)	276,637	(294,951)	1
Balance, beginning (in shares) at Jun. 30, 2018	29,048,589	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock, net of issuance costs	$ 1		3,891
Issuance of common stock, net of issuance costs (in shares)	651,525
Issuance of common stock upon RSU conversion	7,597
Payroll tax withheld for RSU releases			(46)
Share-based compensation expense			849
Net unrealized gain (loss) on investments					(1)	(1)
Net loss				(12,695)		(12,695)
Balance, ending at Sep. 30, 2018	$ 30	$ (352)	281,331	(307,646)		(26,637)
Balance, ending (in shares) at Sep. 30, 2018	29,707,711	(33,801)
Balance, beginning at Dec. 31, 2018	$ 50	$ (352)	325,130	(316,983)		7,845
Balance, beginning (in shares) at Dec. 31, 2018	49,710,104	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	18,765
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			2,532
Net loss				(13,414)		(13,414)
Balance, ending at Sep. 30, 2019	$ 50	$ (352)	327,671	(330,397)		(3,028)
Balance, ending (in shares) at Sep. 30, 2019	49,764,909	(33,801)
Balance, beginning at Jun. 30, 2019	$ 50	$ (352)	327,035	(328,346)	1
Balance, beginning (in shares) at Jun. 30, 2019	49,764,076	(33,801)
Increase (Decrease) in Stockholders Equity
Shares issued for exercise of stock options (in shares)	833
Share-based compensation expense			636
Net unrealized gain (loss) on investments					$ (1)	(1)
Net loss				(2,051)		(2,051)
Balance, ending at Sep. 30, 2019	$ 50	$ (352)	$ 327,671	$ (330,397)		$ (3,028)
Balance, ending (in shares) at Sep. 30, 2019	49,764,909	(33,801)