Note 7 - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income tax at federal statutory rate	$ 241,571	$ 211,610	$ 193,749
State tax, net of federal effect	18,671	17,357	13,551
Nondeductible meals and entertainment	1,420	1,395	1,543
Change in effective state tax rate, net of federal benefit	$ 1,761	$ 256	3,708
Change in valuation allowance			(755)
Other, net	$ (455)	$ (809)	(610)
Total tax expense	$ 262,968	$ 229,809	$ 211,186