Note 14 - Business Segment, Geographic and Quarterly Financial Data - Geographic Segment Financial Data (Details) - USD ($) $ 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
Assets	30,088				32,224				30,088	32,224
UNITED STATES
Revenues									18,622	25,882
Assets	24,524				23,460				24,524	23,460
Non-US [Member]
Revenues									3,928	4,585
Assets	$ 5,564				$ 8,764				$ 5,564	$ 8,764