Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Total
Balance	$ 86	$ 518,027	$ (429,326)	$ 88,787
Balance (in shares) at Dec. 31, 2018	8,640,583
Balance at Dec. 31, 2018	$ 86	518,027	(429,326)	88,787
Issuance of common stock, net of issue costs (in shares)	3,244,941
Issuance of common stock, net of issue costs	$ 33	9,611		9,644
Non-cash stock-based compensation		234		234
Net loss			(6,136)	(6,136)
Balance (in shares) at Mar. 31, 2019	11,885,524
Balance	$ 119	527,872	(435,462)	92,529
Balance at Mar. 31, 2019	$ 119	527,872	(435,462)	92,529
Balance (in shares) at Dec. 31, 2018	8,640,583
Balance at Dec. 31, 2018	$ 86	518,027	(429,326)	88,787
Net loss				(21,845)
Balance (in shares) at Sep. 30, 2019	13,369,001
Balance	$ 133	527,958	(451,171)	76,920
Balance at Sep. 30, 2019	133	527,958	(451,171)	76,920
Balance	$ 119	527,872	(435,462)	92,529
Balance (in shares) at Mar. 31, 2019	11,885,524
Balance at Mar. 31, 2019	$ 119	527,872	(435,462)	92,529
Issuance of common stock, net of issue costs		(14)		(14)
Non-cash stock-based compensation		172		172
Net loss			(7,090)	(7,090)
Balance (in shares) at Jun. 30, 2019	11,885,524
Balance	$ 119	528,030	(442,552)	85,597
Balance at Jun. 30, 2019	119	528,030	(442,552)	85,597
Balance	119	528,030	(442,552)	85,597
Issuance of common stock, net of issue costs		(161)		(161)
Non-cash stock-based compensation		304		304
Issuance of common stock under stock plans, net of taxes (in shares)	1,483,477
Issuance of common stock under stock plans, net of taxes	$ 14	(215)		(201)
Net loss			(8,619)	(8,619)
Balance (in shares) at Sep. 30, 2019	13,369,001
Balance	$ 133	527,958	(451,171)	76,920
Balance at Sep. 30, 2019	133	527,958	(451,171)	76,920
Balance	133	527,958	(451,171)	76,920
Balance	$ 141	530,349	(457,986)	72,504
Balance (in shares) at Dec. 31, 2019	14,083,232
Balance at Dec. 31, 2019	$ 141	530,349	(457,986)	72,504
Issuance of common stock, net of issue costs (in shares)	425,776
Issuance of common stock, net of issue costs	$ 4	902		906
Non-cash stock-based compensation		336		336
Issuance of common stock under stock plans, net of taxes (in shares)	105,882
Issuance of common stock under stock plans, net of taxes
Net loss			(9,253)	(9,253)
Balance (in shares) at Mar. 31, 2020	14,614,890
Balance	$ 145	531,587	(467,239)	64,493
Balance at Mar. 31, 2020	$ 145	531,587	(467,239)	64,493
Balance (in shares) at Dec. 31, 2019	14,083,232
Balance at Dec. 31, 2019	$ 141	530,349	(457,986)	72,504
Net loss				$ (22,132)
Issuance of common stock upon exercise of warrants (in shares)				52,953,400
Balance (in shares) at Sep. 30, 2020	119,578,203
Balance	$ 1,196	613,511	(480,118)	$ 72,504
Balance at Sep. 30, 2020	1,196	613,511	(480,118)	134,589
Balance	$ 145	531,587	(467,239)	64,493
Balance (in shares) at Mar. 31, 2020	14,614,890
Balance at Mar. 31, 2020	$ 145	531,587	(467,239)	64,493
Issuance of common stock, net of issue costs (in shares)	917,345
Issuance of common stock, net of issue costs	$ 9	1,238		1,247
Non-cash stock-based compensation		497		497
Issuance of common stock under stock plans, net of taxes (in shares)	(18,137)
Issuance of common stock under stock plans, net of taxes		(307)		(307)
Net loss			(6,043)	(6,043)
Balance (in shares) at Jun. 30, 2020	15,514,098
Balance	$ 154	533,015	(473,282)	59,887
Balance at Jun. 30, 2020	154	533,015	(473,282)	59,887
Balance	154	533,015	(473,282)	59,887
Non-cash stock-based compensation		642		642
Issuance of common stock under stock plans, net of taxes (in shares)	4,066,862
Issuance of common stock under stock plans, net of taxes	$ 41	(62)		(21)
Net loss			(6,836)	(6,836)
Issuance of common stock and common stock warrants, net of issue costs (in shares)	42,772,687
Issuance of common stock and common stock warrants, net of issue costs	$ 428	61,265		61,693
Issuance of common stock upon exercise of warrants (in shares)	52,953,400
Issuance of common stock upon exercise of warrants	$ 530	16,117		16,647
Issuance of common stock upon conversion of 2020/21 Notes (in shares)	4,169,426
Issuance of common stock upon conversion of 2020/21 Notes	$ 42	2,441		2,483
Issuance of common stock in exchange for services rendered (in shares)	101,730
Issuance of common stock in exchange for services rendered	$ 1	93		94
Balance (in shares) at Sep. 30, 2020	119,578,203
Balance	$ 1,196	613,511	(480,118)	59,887
Balance at Sep. 30, 2020	1,196	613,511	(480,118)	134,589
Balance	$ 1,196	$ 613,511	$ (480,118)	$ 134,589