Consolidated Statements of Stockholders' Equity - 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, 2018	8,640,583
Balance at Dec. 31, 2018	$ 86	$ 518,027	$ 0	$ (429,326)	$ 88,787
Issuance of common stock, net of issue costs (in shares)	3,965,688
Issuance of common stock, net of issue costs	$ 40	11,317	0	0	11,357
Non-cash stock-based compensation	$ 0	1,221	0	0	1,221
Issuance of common stock under stock plans, net of taxes (in shares)	1,476,961
Issuance of common stock under stock plans, net of taxes	$ 15	(216)	0	0	(201)
Net loss	$ 0	0	0	(28,660)	(28,660)
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	2,101	0	0	2,101
Issuance of common stock under stock plans, net of taxes (in shares)	4,142,061
Issuance of common stock under stock plans, net of taxes	$ 41	(391)	0	0	(350)
Net loss	$ 0	0	0	(40,186)	(40,186)
Issuance of common stock and common stock warrants, net of issue costs (in shares)	46,290,808
Issuance of common stock and common stock warrants, net of issue costs	$ 463	69,614	0	0	$ 70,077
Issuance of common stock upon exercise of warrants (in shares)	53,678,400				53,678,400
Issuance of common stock upon exercise of warrants	$ 537	16,545	0	0	$ 17,082
Issuance of common stock upon conversion of 2020/21 Notes (in shares)	9,842,080
Issuance of common stock upon conversion of 2020/21 Notes	$ 99	24,958	0	0	25,057
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 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	456,765	0	0	457,447
Non-cash stock-based compensation	$ 0	7,700	0	0	7,700
Issuance of common stock under stock plans, net of taxes (in shares)	3,813,014
Issuance of common stock under stock plans, net of taxes	$ 38	(5,613)	0	0	(5,575)
Net loss	$ 0	0	0	(59,203)	(59,203)
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
Other comprehensive loss	$ 0	0	(614)	0	(614)
Balance (in shares) at Dec. 31, 2021	201,988,662
Balance at Dec. 31, 2021	$ 2,020	$ 1,103,224	$ (614)	$ (557,375)	$ 547,255