Note 12 - Segment and Enterprise-wide Disclosures - Net Sales to Unaffiliated Customers by Geography (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net sales	$ 37,548	$ 36,416	$ 24,851	$ 30,551	$ 30,170	$ 29,100	$ 29,483	$ 28,479	$ 129,366	$ 117,232	$ 105,568
UNITED STATES
Net sales									75,222	63,130	59,078
GERMANY
Net sales									12,365	12,400	12,445
Other Countries [Member]
Net sales									$ 41,779	$ 41,702	$ 34,045