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, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Net sales by geographic region
Consolidated sales	$ 18,154,000	$ 18,154,000	$ 12,304,000
Long-lived assets by geographic region
Consolidated total long-lived assets	4,050,000	4,050,000		$ 3,943,000
Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	18,154,000
UNITED STATES
Long-lived assets by geographic region
Consolidated total long-lived assets	2,564,000	2,564,000		2,450,000
UNITED STATES | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	15,619,000		12,040,000
International Member
Long-lived assets by geographic region
Consolidated total long-lived assets	1,486,000	$ 1,486,000		$ 1,493,000
International Member | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	$ 2,535,000		$ 264,000