Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Percent, Total	(3.70%)	(0.50%)	23.90%
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount			$ 6,200
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 4,800	$ 8,200
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	700	600
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	100	20	$ 200
Decrease in Unrecognized Tax Benefits is Reasonably Possible	1,700
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	360	$ 1,174
Operating Loss Carryforwards, Total	$ 4,100
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Income Tax Examination, Year under Examination	2013 2014