Note 11 - Business Segment and Geographic Financial Data - Geographic Segment Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenues	$ 7,559	$ 8,155	$ 17,810	$ 16,334
Assets	51,039		51,039		$ 30,088
UNITED STATES
Revenues	6,049	6,473	15,100	12,880
Assets	46,713		46,713		24,524
Non-US [Member]
Revenues	1,510	$ 1,682	2,710	$ 3,454
Assets	$ 4,326		$ 4,326		$ 5,564