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, 2018	$ 7	$ 232,243	$ (197,304)	$ (4)
Balance (in shares) at Dec. 31, 2018	7,141,996
Increase (Decrease) in Shareholders' Equity
Issuance of common stock for at-the-market offerings		2,045
Issuance of common stock for at-the-market offerings (in shares)	353,746
Issuance of common stock and warrants in public offerings	$ 4	18,501
Issuance of common stock and warrants in public offerings (in shares)	4,000,000
Issuance of common stock upon exercise of common stock options and warrants		3
Issuance of common stock upon exercise of common stock options and warrants (in shares)	500
Stock-based compensation expense		408
Realized (loss) 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
Balance at Dec. 31, 2019	$ 12	259,305	(223,597)		$ 35,720
Balance (in shares) at Dec. 31, 2019	12,433,600				12,433,600
Increase (Decrease) in Shareholders' Equity
Issuance of common stock for at-the-market offerings	$ 1	1,059
Issuance of common stock for at-the-market offerings (in shares)	173,572
Issuance of common stock and warrants in public offerings	$ 5	24,554
Issuance of common stock and warrants in public offerings (in shares)	5,290,000
Stock-based compensation expense		339
Realized (loss) gain on short-term investments				(15)	$ (15)
Net loss			(7,952)		(7,952)
Balance at Mar. 31, 2020	$ 18	$ 285,257	$ (231,549)	$ (15)	$ 53,711
Balance (in shares) at Mar. 31, 2020	17,897,172				17,897,172