Note 9 - Equity, Share-based Compensation and Warrants - Stockholders Equity (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Balance (in shares)		51,589,674			51,589,674
Balance	$ 17,225	$ 18,495	$ 24,261	$ 23,420	$ 18,495	$ 23,420
Common stock awards under equity incentive plans	146	241	290	250
Common stock issued to vendor	1	5	5	3
Net income (loss)	(2,621)	(1,516)	(1,923)	591	(4,137)	(1,332)
Net income (loss)	$ (2,621)	(1,516)	(1,923)	591	$ (4,137)	(1,332)
Balance (in shares)	52,310,304				52,310,304
Balance	$ 14,751	17,225	22,807	24,261	$ 14,751	22,807
Other			3	(3)
Exercise of common stock warrants			171
Preferred Stock [Member]
Balance	75	75	112	112	75	112
Common stock awards under equity incentive plans	0	0	0	0
Common stock issued to vendor	0	0	0	0
Net income (loss)	0	0	0	0
Net income (loss)	0	0	0	0
Balance	$ 75	$ 75	112	112	$ 75	$ 112
Other			0	$ 0
Exercise of common stock warrants			$ 0
Preferred Stock [Member] | Series G Preferred Stock [Member]
Balance (in shares)	150	150	225	225	150	225
Common stock awards under equity incentive plans (in shares)	0	0	0	0
Common stock issued to vendor (in shares)	0	0	0	0
Balance (in shares)	150	150	225	225	150	225
Exercise of common stock warrants (in shares)			0
Common Stock [Member]
Balance (in shares)	51,820,425	51,589,674	45,274,030	45,238,087	51,589,674	45,238,087
Balance	$ 326,525	$ 326,279	$ 322,468	$ 322,218	$ 326,279	$ 322,218
Common stock awards under equity incentive plans (in shares)	483,879	224,751	29,643	29,943
Common stock awards under equity incentive plans	$ 146	$ 241	$ 290	$ 250
Common stock issued to vendor (in shares)	6,000	6,000	6,000	6,000
Common stock issued to vendor	$ 1	$ 5	$ 5	$ 3
Net income (loss)	0	0	0	0
Net income (loss)	$ 0	$ 0	$ 0	$ 0
Balance (in shares)	52,310,304	51,820,425	45,487,609	45,274,030	52,310,304	45,487,609
Balance	$ 326,672	$ 326,525	$ 322,937	$ 322,468	$ 326,672	$ 322,937
Other			$ 3	(3)
Exercise of common stock warrants (in shares)			177,936
Exercise of common stock warrants			$ 171
Retained Earnings [Member]
Balance	(309,375)	(307,859)	(298,319)	(298,910)	(307,859)	(298,910)
Common stock awards under equity incentive plans	0	0	0	0
Common stock issued to vendor	0	0	0	0
Net income (loss)	(2,621)	(1,516)	(1,923)	591
Net income (loss)	(2,621)	(1,516)	(1,923)	591
Balance	$ (311,996)	$ (309,375)	(300,242)	(298,319)	$ (311,996)	$ (300,242)
Other			0	$ 0
Exercise of common stock warrants			$ 0