Note 17 - Unaudited Quarterly Financial Data - Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Revenues	$ 6,216	$ 8,155	$ 4,401	$ 3,778	$ 4,912	$ 6,452	$ 8,948	$ 10,155	$ 22,550	$ 30,467
Cost of sales	3,613	2,249	3,799	2,251	4,883	3,563	5,050	6,141	11,912	19,637
Net (loss) income from continuing operations	(1,543)	2,376	(2,544)	(2,567)	(4,340)	(1,296)	(936)	(1,279)	(4,278)	(7,851)
Loss from discontinued operations (net of income tax benefit of $0 in 2020 and 2019)						18	(9)	(10)		(1)
Net loss	$ (1,543)	$ 2,376	$ (2,544)	$ (2,567)	$ (4,340)	$ (1,278)	$ (945)	$ (1,289)	$ (4,278)	$ (7,852)
Continuing operations (in dollars per share)	$ (0.07)	$ 0.10	$ (0.10)	$ (0.10)	$ (0.18)	$ (0.05)	$ (0.04)	$ (0.05)	$ (0.17)	$ (0.32)
Discontinued operations (in dollars per share)										0
Basic net (loss) income per common share: (in dollars per share)	(0.07)	0.10	(0.10)	(0.10)	(0.18)	(0.05)	(0.04)	(0.05)	(0.17)	(0.32)
Continuing operations (in dollars per share)	(0.07)	0.09	(0.10)	(0.10)	(0.18)	(0.05)	(0.04)	(0.05)	(0.17)	(0.32)
Discontinued operations (in dollars per share)
Diluted net (loss) income per common share: (in dollars per share)	$ (0.07)	$ 0.09	$ (0.10)	$ (0.10)	$ (0.18)	$ (0.05)	$ (0.04)	$ (0.05)	$ (0.17)	$ (0.32)