Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Total
Beginning Balance (in shares) at Dec. 31, 2015	54,018
Beginning Balance at Dec. 31, 2015	$ 1	$ 387,817	$ (339,492)	$ 48,326
Issuance of common stock under stock plans, net (in shares)	139
Issuance of common stock under stock plans, net
Issuance of common stock, net of issue costs & warrants (in shares)	124,005
Issuance of common stock, net of issue costs & warrants	$ 1	34,223		34,224
Non-cash stock-based compensation		886		886
Issuance of common stock upon exercise of warrants (in shares)	127,961
Issuance of common stock upon exercise of warrants	$ 1	12,297		12,298
Issuance of common stock upon exchange or conversion of debt (in shares)	47,589
Issuance of common stock upon exchange or conversion of debt		10,758		10,758
Net loss			(37,228)	(37,228)
Ending Balance (in shares) at Dec. 31, 2016	353,712
Ending Balance at Dec. 31, 2016	$ 4	445,980	(376,720)	69,264
Issuance of common stock under stock plans, net (in shares)	150
Issuance of common stock under stock plans, net
Issuance of common stock, net of issue costs & warrants (in shares)	284,000
Issuance of common stock, net of issue costs & warrants	$ 3	6,392		6,395
Non-cash stock-based compensation		421		421
Issuance of common stock upon exercise of warrants (in shares)	308,000
Issuance of common stock upon exercise of warrants	$ 3	3,426		3,429
Issuance of common stock upon exchange or conversion of debt (in shares)	144,691
Issuance of common stock upon exchange or conversion of debt	$ 1	8,651		8,652
Net loss			(24,630)	(24,630)
Ending Balance (in shares) at Dec. 31, 2017	1,090,553
Ending Balance at Dec. 31, 2017	$ 11	464,870	(401,350)	63,531
Issuance of common stock under stock plans, net (in shares)	119
Issuance of common stock under stock plans, net
Issuance of common stock, net of issue costs & warrants (in shares)	6,936,930
Issuance of common stock, net of issue costs & warrants	$ 69	38,877		38,946
Non-cash stock-based compensation		571		$ 571
Issuance of common stock upon exercise of warrants (in shares)	300,911			300,911
Issuance of common stock upon exercise of warrants	$ 3	6,165		$ 6,168
Issuance of common stock upon exchange or conversion of debt (in shares)	299,809
Issuance of common stock upon exchange or conversion of debt	$ 3	7,544		7,547
Net loss			(27,976)	(27,976)
Shares issued upon reverse stock split (in shares)	12,261
Ending Balance (in shares) at Dec. 31, 2018	8,640,583
Ending Balance at Dec. 31, 2018	$ 86	$ 518,027	$ (429,326)	$ 88,787