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, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Net sales by geographic region
Consolidated sales	$ 25,500,000	$ 25,500,000	$ 11,415,000	$ 43,654,000	$ 23,718,000
Long-lived assets by geographic region
Consolidated total long-lived assets	4,004,000	4,004,000		4,004,000		$ 3,943,000
Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales		25,500,000
UNITED STATES
Long-lived assets by geographic region
Consolidated total long-lived assets	2,544,000	2,544,000		2,544,000		2,450,000
UNITED STATES | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales		22,546,000	11,158,000	38,165,000	23,197,000
International Member
Long-lived assets by geographic region
Consolidated total long-lived assets	$ 1,460,000	1,460,000		1,460,000		$ 1,493,000
International Member | Reportable Geographical Components [Member]
Net sales by geographic region
Consolidated sales		$ 2,954,000	$ 257,000	$ 5,489,000	$ 521,000