Note 11 - Business Segment and Geographic Financial Data - Geographic Segment Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenues	$ 5,218	$ 4,401	$ 10,251	$ 8,179
Assets	50,061		50,061		$ 30,088
UNITED STATES
Revenues	4,588	3,310	9,051	6,407
Assets	46,186		46,186		24,524
Non-US [Member]
Revenues	630	$ 1,091	1,200	$ 1,772
Assets	$ 3,875		$ 3,875		$ 5,564