Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Preferred Stock Series B convertible preferred stock	Preferred Stock Series C convertible preferred stock	Preferred Stock Series E convertible preferred stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2018		$ 1			$ 450,652	$ (418,990)		$ 31,663
Balance (in shares) at Dec. 31, 2018	159	95,388		73,092
Changes in Stockholders' (Deficit) Equity
Net loss						(4,476)		(4,476)
Stock-based compensation expense					1,256			1,256
Issuance of warrants expense					130			130
Conversion of common stock into convertible preferred stock			$ 12		(12)
Conversion of common stock into convertible preferred stock (in shares)			1,192,000	(9,933)
Conversion of convertible preferred stock into common stock (in shares)	(156)			1,040
Balance at Mar. 31, 2019		$ 1	$ 12		452,026	(423,466)		28,573
Balance (in shares) at Mar. 31, 2019	3	95,388	1,192,000	64,199
Balance at Dec. 31, 2019		$ 1			517,311	(493,197)	$ (8)	24,107
Balance (in shares) at Dec. 31, 2019	3	95,388		391,739
Changes in Stockholders' (Deficit) Equity
Net loss						(4,311)		(4,311)
Other comprehensive loss, net of tax							(48)	(48)
Stock-based compensation expense					427			427
Issuance of warrants expense					1,393			1,393
Balance at Mar. 31, 2020		$ 1			$ 519,131	$ (497,508)	$ (56)	$ 21,568
Balance (in shares) at Mar. 31, 2020	3	95,388		391,739