Note 11 - Financial Information about Geographic Areas - Consolidated Net Sales and Long-lived Asset Information by Geographic Area (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Net sales by geographic region
Consolidated sales	$ 14,475,000	$ 30,027,000	$ 55,442,000	$ 73,681,000
Long-lived assets by geographic region
Consolidated total long-lived assets	6,136,000		6,136,000		$ 4,353,000
Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	14,475,000
UNITED STATES
Long-lived assets by geographic region
Consolidated total long-lived assets	4,668,000		4,668,000		2,787,000
UNITED STATES | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	14,244,000	24,295,000	52,836,000	62,461,000
International Member
Long-lived assets by geographic region
Consolidated total long-lived assets	1,468,000		1,468,000		$ 1,566,000
International Member | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales	$ 231,000	$ 5,732,000	$ 2,606,000	$ 11,220,000