CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balance at Dec. 31, 2017	$ 41	$ 202,790		$ (96)	$ (144,727)	$ 58,008
Balance (in shares) at Dec. 31, 2017	40,549,936		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense		1,127				1,127
Unrealized loss on investments				(11)		(11)
Net loss					(5,999)	(5,999)
Balance at Mar. 31, 2018	$ 41	203,917		(107)	(150,726)	53,125
Balance (in shares) at Mar. 31, 2018	40,549,936		29,231
Balance at Dec. 31, 2018	$ 53	249,727		(2)	(181,453)	68,325
Balance (in shares) at Dec. 31, 2018	52,548,244		29,231
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense		1,836				1,836
Exercise of stock options		65				65
Exercise of stock options (in shares)	55,812
Forfeiture of restricted stock (in shares)	(20,200)
Unrealized loss on investments				$ 2		2
Net loss					(12,483)	(12,483)
Balance at Mar. 31, 2019	$ 53	$ 251,628			$ (193,936)	$ 57,745
Balance (in shares) at Mar. 31, 2019	52,583,856		29,231