Note 10 - Customer and Geographic Information - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues	$ 21,158	$ 20,541
Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Revenues	$ 21,158	$ 20,541
Percentage of Revenues	100.00%	100.00%
Concentration risk	100.00%	100.00%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | UNITED STATES
Revenues	$ 8,617	$ 9,315
Percentage of Revenues	41.00%	45.00%
Concentration risk	41.00%	45.00%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | CHINA
Revenues	$ 2,959	$ 2,983
Percentage of Revenues	14.00%	15.00%
Concentration risk	14.00%	15.00%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | TAIWAN, PROVINCE OF CHINA
Revenues	$ 2,668	$ 1,755
Percentage of Revenues	12.00%	9.00%
Concentration risk	12.00%	9.00%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Rest of the World [Member]
Revenues	$ 6,914	$ 6,488
Percentage of Revenues	33.00%	31.00%
Concentration risk	33.00%	31.00%