Note 11 - Income Taxes (Detail) - Reconciliation of income tax provision (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Federal income taxes due at statutory rate	$ 37,295	$ 42,285	$ 45,998
Reductions in income taxes resulting from:
Interest on state and municipal securities and loans not taxable for federal income tax purposes	(12,494)	(12,423)	(11,875)
State franchise taxes, net of federal income tax benefit	6,722	8,252	8,104
Tax credits	(3,684)	(3,560)	(3,521)
Dividend received deduction	(28)	(25)	(21)
Cash value life insurance	(953)	(728)	(953)
Other	(1,428)	(873)	(887)
Provision for income taxes	$ 25,430	$ 32,928	$ 36,845

The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to the deduction for dividends paid or received under enacted tax laws.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to income that is exempt from income taxes under enacted tax laws.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to increases in the the cash value of life insurance which is exempt from income taxes under enacted tax laws.

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