STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ 10,275	$ 1	$ 141,277	$ (2)	$ (131,001)
Beginning Balance, shares at Dec. 31, 2017		654,170
Issuance of common stock for cash, net of offering costs	3,415		3,415
Issuance of common stock for cash, net of offering costs, shares		118,546
Issuance of common stock upon vesting of Restricted Stock Units, value	0	$ 0	0	0	0
Issuance of common stock upon vesting of Restricted Stock Units, shares		301
Share-based compensation	97		97
Change in unrealized loss on marketable securities	2			2
Net loss	(2,735)				(2,735)
Ending Balance at Mar. 31, 2018	11,054	$ 1	144,789		(133,736)
Ending Balance, shares at Mar. 31, 2018		773,017
Beginning Balance at Dec. 31, 2017	10,275	$ 1	141,277	(2)	(131,001)
Beginning Balance, shares at Dec. 31, 2017		654,170
Change in unrealized loss on marketable securities	2
Net loss	(6,444)
Ending Balance at Sep. 30, 2018	7,463	$ 1	144,907		(137,445)
Ending Balance, shares at Sep. 30, 2018		773,545
Beginning Balance at Mar. 31, 2018	11,054	$ 1	144,789		(133,736)
Beginning Balance, shares at Mar. 31, 2018		773,017
Issuance of common stock upon vesting of Restricted Stock Units, value	0	$ 0	0	0	0
Issuance of common stock upon vesting of Restricted Stock Units, shares		528
Share-based compensation	60		60
Net loss	(2,116)				(2,116)
Ending Balance at Jun. 30, 2018	8,998	$ 1	144,849		(135,852)
Ending Balance, shares at Jun. 30, 2018		773,545
Share-based compensation	58		58
Net loss	(1,593)				(1,593)
Ending Balance at Sep. 30, 2018	7,463	$ 1	144,907		(137,445)
Ending Balance, shares at Sep. 30, 2018		773,545
Issuance of common stock upon vesting of Restricted Stock Units, value	0	$ 0	0	$ 0	0
Issuance of common stock upon vesting of Restricted Stock Units, shares		13
Share-based compensation	58		58
Net loss	(1,489)				(1,489)
Ending Balance at Dec. 31, 2018	$ 6,032	$ 1	144,965		(138,934)
Ending Balance, shares at Dec. 31, 2018	773,558	773,558
Issuance of common stock for cash, net of offering costs	$ 2,900		2,900
Issuance of common stock for cash, net of offering costs, shares		325,304
Share-based compensation	50		50
Adjustment for fractional shares		(49)
Net loss	(1,664)				(1,664)
Ending Balance at Mar. 31, 2019	7,318	$ 1	147,915		(140,598)
Ending Balance, shares at Mar. 31, 2019		1,098,813
Beginning Balance at Dec. 31, 2018	$ 6,032	$ 1	144,965		(138,934)
Beginning Balance, shares at Dec. 31, 2018	773,558	773,558
Net loss	$ (4,256)
Ending Balance at Sep. 30, 2019	$ 8,799	$ 2	151,987		(143,190)
Ending Balance, shares at Sep. 30, 2019	1,594,070	1,594,070
Beginning Balance at Mar. 31, 2019	$ 7,318	$ 1	147,915		(140,598)
Beginning Balance, shares at Mar. 31, 2019		1,098,813
Issuance of common stock for cash, net of offering costs	3,262		3,262
Issuance of common stock for cash, net of offering costs, shares		356,743
Share-based compensation	45		45
Net loss	(1,436)				(1,436)
Ending Balance at Jun. 30, 2019	9,189	$ 1	151,222		(142,034)
Ending Balance, shares at Jun. 30, 2019		1,455,556
Issuance of common stock for cash, net of offering costs	737	$ 1	736
Issuance of common stock for cash, net of offering costs, shares		138,514
Share-based compensation	29		29
Net loss	(1,156)				(1,156)
Ending Balance at Sep. 30, 2019	$ 8,799	$ 2	$ 151,987		$ (143,190)
Ending Balance, shares at Sep. 30, 2019	1,594,070	1,594,070