Note 3 - Intangible Assets - Aggregate Intangible Asset Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Intangible asset amortization expense	$ 75	$ 72	$ 150	$ 144
Cost of Sales [Member]
Intangible asset amortization expense	35	31	70	63
Selling, General and Administrative Expenses [Member]
Intangible asset amortization expense	$ 40	$ 41	$ 80	$ 81