Income Taxes (Tables)

12 Months Ended

Dec. 31, 2012

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

Income tax expense is comprised of the following:

	Years Ended December 31,
	2012		2011			2010
Taxes currently payable
Federal	$	45,683	$	45,026		$	5,188
State	2,655		1,823			1,460
Deferred (benefit) expense	4,679		(756		)	30,443
	$	53,017	$	46,093		$	37,091

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

		Years Ended December 31,
		2012		2011		2010
Statutory rate		35.00	%	35.00	%	35.00	%
Increase (decrease) in rate due to:
	Interest on tax-exempt securities and tax-free loans, net	(3.23	)	(3.04	)	(3.36	)
	Bank owned life insurance	(3.10	)	(3.26	)	(3.94	)
	State income tax (net)	0.94		0.72		0.68
	Tax credits	(2.15	)	(2.12	)	(2.37	)
	ESOP Dividends	(0.21	)	(0.24	)	(0.29	)
	Non-deductible meals and entertainment	0.25		0.29		0.30
	Other	0.83		0.48		0.47
Effective tax rates		28.33	%	27.83	%	26.49	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

Principal components of the Corporation's net deferred tax asset are summarized as follows:

		Twelve Months Ended
		December 31,
		2012			2011
Deferred tax assets:
	Allowance for credit losses	$	37,341		$	42,481
	Employee benefits	42,934			44,572
	REMIC	6,201			6,749
	Acquired liabilities	5,041			5,576
	Goodwill	2,838			13,041
	Core deposit intangible	1,275			1,066
	Other	—			1,875
		95,630			115,360
Deferred tax liabilities:
	Leased assets and depreciation	(6,962		)	(4,776		)
	Acquired loans	(18,765		)	(35,533		)
	Available for sale securities	(29,841		)	(28,929		)
	FHLB stock	(25,577		)	(25,577		)
	Loan fees and expenses	(5,709		)	(4,618		)
	Other	(1,665		)	—
		(88,519		)	(99,433		)
Total net deferred tax asset		$	7,111		$	15,927

Change in Deferred Taxes [Table Text Block]

		Twelve Months Ended
		December 31,
		2012		2011
Deferred tax changes reflected in other comprehensive income		$	4,137	$	1,193
Deferred tax changes reflected in Federal income tax expense		4,679		(756		)
	Net change in deferred taxes	$	8,816	$	437

Summary of Income Tax Contingencies [Table Text Block]

A reconciliation of the change in the reserve for uncertain tax positions is as follows:

	Federal and State Tax			Accrued Interest and Penalties			Gross Unrecognized Income Tax Benefits
Balance at January 1, 2012	$	946		$	1,491		$	2,437
Additions for tax provisions related to prior year	74			621			695
Reduction for tax positions related to prior year due closed tax years	(28		)	(44		)	(72		)
Reduction for tax positions related to prior tax years	(39		)	(1,214		)	(1,253		)
Balance at December 31, 2012	$	953		$	854		$	1,807
Components of Reserve:
Potential adjustment to non-deductible interest expense	$	30		$	4		$	34
Timing of the accrual for interest on nonperforming assets	—			631			631
State income tax exposure	923			219			1,142
Balance at December 31, 2012	$	953		$	854		$	1,807
	Federal and State Tax			Accrued Interest and Penalties			Gross Unrecognized Income Tax Benefits
Balance at January 1, 2011	$	979		$	801		$	1,780
Additions for tax provisions related to prior year	18			1,414			1,432
Reduction for tax positions related to prior year due closed tax years	(44		)	(598		)	(642		)
Reduction for tax positions related to prior tax years	(7		)	(126		)	(133		)
Balance at December 31, 2011	$	946		$	1,491		$	2,437
Components of Reserve:
Potential adjustment to non-deductible interest expense	$	58		$	9		$	67
Timing of the accrual for interest on nonperforming assets	—			1,175			1,175
State income tax exposure	888			307			1,195
Balance at December 31, 2011	$	946		$	1,491		$	2,437