Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Income Tax Expense (Benefit)		$ 1,445	$ 1,408	$ 3,112	$ 2,678
Effective Income Tax Rate Reconciliation, Percent		5.80%	8.90%	5.50%	6.90%
Unrecognized Tax Benefits		$ 16,100		$ 16,100		$ 14,400
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		4,500		4,500		3,500
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		$ 500		$ 500		$ 300
Scenario, Forecast [Member]
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	$ 600