CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Series C Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]
Beginning Balance at Dec. 31, 2017	$ (7,041)	$ 10,508	$ 5,000			$ 5,394	$ (12,435)
Beginning Balance (shares) at Dec. 31, 2017		21,302,972	1,937,984		3,804,643
Beginning Balance (shares) at Dec. 31, 2017								105,144
Stock-based compensation	135					135
Series C convertible preferred stock				$ 21,000
Series C convertible preferred stock (shares)				4,606,267
Issuance costs for Series C preferred				$ (7)
Net loss	(1,847)						(1,847)
Ending Balance at Mar. 31, 2018	(8,753)					5,529	(14,282)		$ 0
Ending Balance (Shares) at Mar. 31, 2018		21,302,972	1,937,984	4,606,267
Ending Balance (Shares) at Mar. 31, 2018					3,804,643			105,144
Ending Balance at Mar. 31, 2018		$ 10,508	$ 5,000	$ 20,993
Beginning Balance at Dec. 31, 2018	89,429				$ 3	122,526	(33,083)		(17)
Beginning Balance (shares) at Dec. 31, 2018					25,809,900			105,144
Stock-based compensation	780					780
Exercise of stock options	3					3
Exercise of stock options (in shares)					3,729
Net loss	(7,479)						(7,479)
Unrealized gain on marketable securities	28								28
Adoption of ASU 2018-07						(98)	98
Ending Balance at Mar. 31, 2019	$ 82,761				$ 3	$ 123,211	$ (40,464)		$ 11
Ending Balance (Shares) at Mar. 31, 2019					25,813,629
Ending Balance (Shares) at Mar. 31, 2019								105,144