Note 13 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent, Total	23.30%	38.80%
Income Tax Expense (Benefit), Total	$ 11,768	$ 14,111
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				35.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Amount, Total	1,200
Deferred Tax Assets, Net, Total	$ 40,500			$ 41,500
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%