Note 11 - Financial Information about Geographic Areas - Consolidated Net Sales and Long-lived Asset Information by Geographic Area (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Net sales by geographic region
Consolidated sales	$ 17,806,000	$ 25,500,000	$ 40,967,000	$ 43,654,000
Long-lived assets by geographic region
Consolidated total long-lived assets	5,422,000		5,422,000		$ 4,353,000
Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	17,806,000
UNITED STATES
Long-lived assets by geographic region
Consolidated total long-lived assets	3,915,000		3,915,000		2,787,000
UNITED STATES | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	17,694,000	22,546,000	38,592,000	38,165,000
International Member
Long-lived assets by geographic region
Consolidated total long-lived assets	1,507,000		1,507,000		$ 1,566,000
International Member | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	$ 112,000	$ 2,954,000	$ 2,375,000	$ 5,489,000