Note 10 - Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Taxes at federal statutory rate									$ 37,106	$ 25,681	$ 25,484
Taxes at federal statutory rate, percentage									35.00%	35.00%	35.00%
Increase (reduction) in taxes resulting from:
State and local income tax, net of Federal income tax benefit									$ 4,890	$ 3,461	$ 4,980
State and local income tax, net of Federal income tax benefit, percentage									4.60%	4.70%	6.80%
Other									$ (893)	$ (1,975)	$ (1,891)
Other, percentage									(0.80%)	(2.70%)	(2.60%)
Total provision for income taxes	$ 8,116	$ 6,655	$ 20,717	$ 5,615	$ 5,439	$ 6,661	$ 9,521	$ 5,546	$ 41,103	$ 27,167	$ 28,573
Taxes at effective rate, percentage									38.80%	37.00%	39.20%