Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2019	14,083,232
Balance at Dec. 31, 2019	$ 141	$ 530,349	$ 0	$ (457,986)	$ 72,504
Non-cash stock-based compensation	$ 0	1,475	0	0	1,475
Issuance of common stock under stock plans, net of taxes (in shares)	4,154,607
Issuance of common stock under stock plans, net of taxes	$ 41	(369)	0	0	(328)
Net loss	$ 0	0	0	(22,132)	(22,132)
Issuance of common stock upon exercise of warrants (in shares)	52,953,400
Issuance of common stock upon exercise of warrants	$ 530	16,117	0	0	16,647
Issuance of common stock and common stock warrants, net of issue costs (in shares)	44,115,808
Issuance of common stock and common stock warrants, net of issue costs	$ 441	63,405	0	0	63,846
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	0	0	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	0	0	94
Balance (in shares) at Sep. 30, 2020	119,578,203
Balance at Sep. 30, 2020	$ 1,196	613,511	0	(480,118)	134,589
Balance (in shares) at Jun. 30, 2020	15,514,098
Balance at Jun. 30, 2020	$ 154	533,015	0	(473,282)	59,887
Non-cash stock-based compensation	$ 0	642	0	0	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)	0	0	(21)
Net loss	$ 0	0	0	(6,836)	(6,836)
Issuance of common stock upon exercise of warrants (in shares)	52,953,400
Issuance of common stock upon exercise of warrants	$ 530	16,117	0	0	16,647
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	0	0	61,693
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	0	0	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	0	0	94
Balance (in shares) at Sep. 30, 2020	119,578,203
Balance at Sep. 30, 2020	$ 1,196	613,511	0	(480,118)	134,589
Balance (in shares) at Dec. 31, 2020	128,138,311
Balance at Dec. 31, 2020	$ 1,282	643,269	0	(498,172)	146,379
Issuance of common stock, net of issue costs (in shares)	68,170,579
Issuance of common stock, net of issue costs	$ 682	456,801	0	0	457,483
Non-cash stock-based compensation	$ 0	3,300	0	0	3,300
Issuance of common stock under stock plans, net of taxes (in shares)	3,704,330
Issuance of common stock under stock plans, net of taxes	$ 37	(5,534)	0	0	(5,497)
Other comprehensive income (loss)	0	0	(296)	0	(296)
Net loss	$ 0	0	0	(42,690)	(42,690)
Issuance of common stock upon exercise of warrants (in shares)	1,866,758
Issuance of common stock upon exercise of warrants	$ 18	1,103	0	0	1,121
Balance (in shares) at Sep. 30, 2021	201,879,978
Balance at Sep. 30, 2021	$ 2,019	1,098,939	(296)	(540,862)	559,800
Balance (in shares) at Jun. 30, 2021	197,964,476
Balance at Jun. 30, 2021	$ 1,980	1,100,932	(307)	(526,482)	576,123
Issuance of common stock, net of issue costs (in shares)	0
Issuance of common stock, net of issue costs	$ 0	(162)	0	0	(162)
Non-cash stock-based compensation	$ 0	1,880	0	0	1,880
Issuance of common stock under stock plans, net of taxes (in shares)	3,915,502
Issuance of common stock under stock plans, net of taxes	$ 39	(3,711)	0	0	(3,672)
Other comprehensive income (loss)	0	0	11	0	11
Net loss	$ 0	0	0	(14,380)	(14,380)
Balance (in shares) at Sep. 30, 2021	201,879,978
Balance at Sep. 30, 2021	$ 2,019	$ 1,098,939	$ (296)	$ (540,862)	$ 559,800