Note 10 - Income Taxes (Details) - Reconciliation of Income Tax Provision (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Income Tax Provision [Abstract]
Federal income taxes due at statutory rate	$ 30,142	$ 37,295	$ 42,285
Reductions in income taxes resulting from:
Interest on state and municipal securities and loans not taxable for federal income tax purposes	(11,565)	(12,494)	(12,423)
State franchise taxes, net of federal income tax benefit	4,712	6,722	8,252
Tax credits	(3,190)	(3,684)	(3,560)
Dividend received deduction	(32)	(28)	(25)
Cash value life insurance	(747)	(953)	(728)
Other	(375)	(1,428)	(873)
Provision for income taxes	$ 18,945	$ 25,430	$ 32,928