Note 10 - Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income tax expense	$ 14,856	$ 47,893	$ 21,256	$ 55,222
Effective income tax rate	26.70%	40.40%	26.00%	40.50%