Note 8 - Segment and Geographic Information - Customers with Sales and Accounts Receivable Greater Than 10% (Details) - Customer Concentration Risk [Member]		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Revenue Benchmark [Member] | Distributor A [Member]
Concentration risk		22.00%	20.00%	22.00%	20.00%
Revenue Benchmark [Member] | Distributor B [Member]
Concentration risk	[1]		10.00%		10.00%
Revenue Benchmark [Member] | End Customer [Member]
Concentration risk		13.00%		10.00%
Accounts Receivable [Member] | Distributor A [Member]
Concentration risk				21.00%		25.00%
Accounts Receivable [Member] | Distributor B [Member]
Concentration risk	[1]			12.00%		16.00%
Accounts Receivable [Member] | End Customer [Member]
Concentration risk				16.00%

[1] Represents less than 10%.