Note 7 - Customer and Geographic Information - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from Contract with Customer, Including Assessed Tax	$ 20,213	$ 26,517	$ 66,069	$ 75,094
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 20,213	$ 26,517	$ 66,069	$ 75,094
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | UNITED STATES
Revenue from Contract with Customer, Including Assessed Tax	$ 8,366	$ 9,750	$ 27,430	$ 30,610
Concentration Risk, Percentage	41.00%	37.00%	42.00%	41.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | CHINA
Revenue from Contract with Customer, Including Assessed Tax	$ 4,644	$ 6,452	$ 14,186	$ 12,891
Concentration Risk, Percentage	23.00%	24.00%	21.00%	17.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | TAIWAN, PROVINCE OF CHINA
Revenue from Contract with Customer, Including Assessed Tax	$ 936	$ 2,414	$ 4,109	$ 9,894
Concentration Risk, Percentage	5.00%	9.00%	6.00%	13.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Rest of the World [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 6,267	$ 7,901	$ 20,344	$ 21,699
Concentration Risk, Percentage	31.00%	30.00%	31.00%	29.00%