Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Total
Balance at Dec. 31, 2017	$ 2	$ 183,223	$ (171,434)		$ 11,791
Balance (in shares) at Dec. 31, 2017	2,364,526
Increase (Decrease) in Shareholders' Equity
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.1 million and $0.3 million for the years 2019 and 2018 respectively	$ 1	8,312			8,313
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.1 million and $0.3 million for the years 2019 and 2018 respectively (in shares)	539,026
Stock-based compensation expense		479			479
Net loss			(7,652)		(7,652)
Balance at Mar. 31, 2018	$ 3	192,014	(179,086)		12,931
Balance (in shares) at Mar. 31, 2018	2,903,552
Balance at Dec. 31, 2018	$ 7	232,243	(197,304)	$ (4)	$ 34,942
Balance (in shares) at Dec. 31, 2018	7,141,996				7,141,996
Increase (Decrease) in Shareholders' Equity
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.1 million and $0.3 million for the years 2019 and 2018 respectively		2,045			$ 2,045
Issuance of common stock for at-the-market offerings, net of issuance costs of $0.1 million and $0.3 million for the years 2019 and 2018 respectively (in shares)	353,746
Issuance of common stock and warrants in public offering, net of issuance costs of $1.5 million	$ 4	18,501			18,505
Issuance of common stock and warrants in public offering, net of issuance costs of $1.5 million (in shares)	4,000,000
Issuance of common stock upon exercise of warrants		3			3
Issuance of common stock upon exercise of warrants (in shares)	500
Stock-based compensation expense		408			408
Realized gain on short-term investments				$ 4	4
Net loss			(6,038)		(6,038)
Balance at Mar. 31, 2019	$ 11	$ 253,200	$ (203,342)		$ 49,869
Balance (in shares) at Mar. 31, 2019	11,496,242				11,496,242