Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Total
Beginning Balance (in shares) at Dec. 31, 2017	1,090,553
Beginning Balance at Dec. 31, 2017	$ 11	$ 464,870	$ (401,350)	$ 63,531
Issuance of common stock, net of issuance costs (in shares)	5,208
Issuance of common stock, net of issuance costs		(107)		(107)
Non-cash stock-based compensation		98		98
Net loss			(2,502)	(2,502)
Issuance of common stock under stock plans, net (in shares)	30
Issuance of common stock under stock plans, net
Issuance of common stock upon exchange of debt (in shares)	39,016
Issuance of common stock upon exchange of debt		528		528
Ending Balance (in shares) at Mar. 31, 2018	1,134,807
Ending Balance at Mar. 31, 2018	$ 11	465,389	(403,852)	61,548
Beginning Balance (in shares) at Dec. 31, 2017	1,090,553
Beginning Balance at Dec. 31, 2017	$ 11	464,870	(401,350)	63,531
Net loss				(13,994)
Ending Balance (in shares) at Jun. 30, 2018	7,990,050
Ending Balance at Jun. 30, 2018	$ 80	514,859	(415,344)	99,595
Beginning Balance (in shares) at Mar. 31, 2018	1,134,807
Beginning Balance at Mar. 31, 2018	$ 11	465,389	(403,852)	61,548
Issuance of common stock, net of issuance costs (in shares)	6,281,409
Issuance of common stock, net of issuance costs	$ 63	36,230		36,293
Non-cash stock-based compensation		61		61
Net loss			(11,492)	(11,492)
Issuance of common stock under stock plans, net (in shares)	19
Issuance of common stock under stock plans, net
Issuance of common stock upon exchange of debt (in shares)	260,793
Issuance of common stock upon exchange of debt	$ 3	7,015		7,018
Shares issued upon reverse stock split (in shares)	12,261
Issuance of common stock upon exercise of warrants (in shares)	300,761
Issuance of common stock upon exercise of warrants	$ 3	6,164		6,167
Ending Balance (in shares) at Jun. 30, 2018	7,990,050
Ending Balance at Jun. 30, 2018	$ 80	514,859	(415,344)	99,595
Beginning Balance (in shares) at Dec. 31, 2018	8,640,583
Beginning Balance at Dec. 31, 2018	$ 86	518,027	(429,326)	88,787
Issuance of common stock, net of issuance costs (in shares)	3,244,941
Issuance of common stock, net of issuance costs	$ 33	9,611		9,644
Non-cash stock-based compensation		234		234
Net loss			(6,136)	(6,136)
Ending Balance (in shares) at Mar. 31, 2019	11,885,524
Ending Balance at Mar. 31, 2019	$ 119	527,872	(435,462)	92,529
Beginning Balance (in shares) at Dec. 31, 2018	8,640,583
Beginning Balance at Dec. 31, 2018	$ 86	518,027	(429,326)	88,787
Net loss				(13,226)
Ending Balance (in shares) at Jun. 30, 2019	11,885,524
Ending Balance at Jun. 30, 2019	$ 119	528,030	(442,552)	85,597
Beginning Balance (in shares) at Mar. 31, 2019	11,885,524
Beginning Balance at Mar. 31, 2019	$ 119	527,872	(435,462)	92,529
Issuance of common stock, net of issuance costs		(14)		(14)
Non-cash stock-based compensation		172		172
Net loss			(7,090)	(7,090)
Ending Balance (in shares) at Jun. 30, 2019	11,885,524
Ending Balance at Jun. 30, 2019	$ 119	$ 528,030	$ (442,552)	$ 85,597