Note 7 - Customer and Geographic Information - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues	$ 21,119	$ 24,289	$ 45,856	$ 48,578
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Revenues	$ 21,119	$ 24,289	$ 45,856	$ 48,578
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | UNITED STATES
Revenues	$ 8,982	$ 9,226	$ 19,065	$ 20,860
Concentration Risk, Percentage	42.00%	38.00%	41.00%	44.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | CHINA
Revenues	$ 4,360	$ 4,753	$ 9,542	$ 6,440
Concentration Risk, Percentage	21.00%	20.00%	21.00%	13.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | TAIWAN, PROVINCE OF CHINA
Revenues	$ 1,038	$ 3,643	$ 3,173	$ 7,480
Concentration Risk, Percentage	5.00%	15.00%	7.00%	15.00%
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member] | Rest of the World [Member]
Revenues	$ 6,739	$ 6,667	$ 14,076	$ 13,798
Concentration Risk, Percentage	32.00%	27.00%	31.00%	28.00%