CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Beginning balance, amount at Dec. 31, 2017	$ 13	$ 356,054	$ (288,900)	$ 67,167
Beginning balance (shares) at Dec. 31, 2017	13,059,341
Share-based compensation, amount		1,627		1,627
Issuance of common stock upon exercise of stock options, amount		73		$ 73
Issuance of common stock upon exercise of stock options (shares)	15,217			15,217
Cancellation of restricted stock	(178,333)
Net loss			(10,279)	$ (10,279)
Ending balance, amount at Mar. 31, 2018	$ 13	357,754	(299,179)	58,588
Ending balance (shares) at Mar. 31, 2018	12,896,225
Beginning balance, amount at Dec. 31, 2018	$ 13	361,218	(327,716)	$ 33,515
Beginning balance (shares) at Dec. 31, 2018	12,960,450			12,960,450
Share-based compensation, amount		551		$ 551
Issuance of common stock upon exercise of stock options, amount		307		$ 307
Issuance of common stock upon exercise of stock options (shares)	156,012			156,012
Net loss			(5,360)	$ (5,360)
Ending balance, amount at Mar. 31, 2019	$ 13	$ 362,076	$ (333,076)	$ 29,013
Ending balance (shares) at Mar. 31, 2019	13,116,462			13,116,462