Note 5 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Income Taxes			$ 1,200
Income Tax Expense (Benefit), Total	$ (439)	$ (815)	$ (820)	$ (1,976)
Effective Income Tax Rate Reconciliation, Percent, Total			23.00%	156.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent						35.00%
Unrecognized Tax Benefits, Ending Balance	13,000		$ 13,000			$ 12,900
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	7,700		7,700			7,700
Unrecognized Tax Benefits In Long Term Liabilities	2,900		2,900
Unrecognized Tax Benefits In Deferred Tax Assets	10,800		10,800
Unrecognized Tax Benefits In Deferred Tax Asset Subject To Full Valuation Allowance	5,300		5,300
Deferred Tax Assets, Valuation Allowance, Total	$ 9,500		$ 9,500			$ 9,100
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					21.00%