Note 11 - Financial Information about Geographic Areas - Consolidated Net Sales and Long-lived Asset Information by Geographic Area (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Net sales by geographic region
Consolidated sales	$ 23,161,000	$ 18,154,000
Long-lived assets by geographic region
Consolidated total long-lived assets	4,287,000		$ 4,353,000
Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	23,161,000
UNITED STATES
Long-lived assets by geographic region
Consolidated total long-lived assets	2,747,000		2,787,000
UNITED STATES | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	20,898,000	15,619,000
International Member
Long-lived assets by geographic region
Consolidated total long-lived assets	1,540,000		$ 1,566,000
International Member | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	$ 2,263,000	$ 2,535,000