Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred tax assets:
Allowance for credit losses	$ 42,481	$ 43,959
Employee benefits	44,572	34,692
REMIC	6,749	7,263
Acquired liabilities	5,576	7,380
Goodwill	13,041	14,314
Core Deposit Intangible	1,066	649
Other	1,875	35
Total Deferred Tax Assets	115,360	108,292
Deferred tax liabilities:
Leased assets and depreciation	(4,776)	(3,381)
Acquired loans	(35,533)	(37,516)
Available for sale securities	(28,929)	(18,697)
FHLB Stock	(25,577)	(25,577)
Loan fees and expenses	(4,618)	(6,757)
Deferred Tax Liabilities	(99,433)	(91,928)
Total net deferred tax asset	15,927	16,364
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Statutory rate	35.00%	35.00%	35.00%
Interest on tax-exempt securities and tax-free loans, net	(3.04%)	(3.36%)	(4.09%)
Bank owned life insurance	(3.26%)	(3.94%)	(4.65%)
State income taxx (net)	0.72%	0.68%	0.15%
Tax Credits	(2.12%)	(2.37%)	(1.97%)
ESOP Dividends	(0.24%)	(0.29%)	(0.49%)
Non-deductible meals and entertainment	0.29%	0.30%	0.28%
Other	0.48%	0.47%	(0.44%)
Effective tax rates	27.83%	26.49%	23.79%
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized Tax Benefits	1,780
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	1,432
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(642)
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	(133)
Unrecognized Tax Benefits	2,437	1,780
Unrecognized Tax Benefits, Potential Adjustment to Non-Deductible Interest Expense	67
Unrecognized Tax Benefits, Timing of Accrual For Interest On Nonperforming Assets	1,175
Unrecognized Tax Benefits, State Income Tax Exposure	1,195
Components of Income Tax Expense (Benefit)
Federal	45,026	5,188	18,291
State	1,823	1,460	237
Deferred (benefit) expense	(756)	30,443	7,117
Income Tax Expense (Benefit)	46,093	37,091	25,645
Net Change In Deferred Taxes [Abstract]
Deferred tax changes reflected in other comprehensive income	1,193	(346)
Deferred tax changes reflected in acquired net assets	0	(21,402)
Deferred Tax, Increase (Decrease) During Period	437	8,695
Federal and State Income Tax [Member]
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized Tax Benefits	979
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	18
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(44)
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	(7)
Unrecognized Tax Benefits	946
Unrecognized Tax Benefits, Potential Adjustment to Non-Deductible Interest Expense	58
Unrecognized Tax Benefits, Timing of Accrual For Interest On Nonperforming Assets	0
Unrecognized Tax Benefits, State Income Tax Exposure	888
Interest and Penalites [Member]
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized Tax Benefits	801
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	1,414
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(598)
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	(126)
Unrecognized Tax Benefits	1,491
Unrecognized Tax Benefits, Potential Adjustment to Non-Deductible Interest Expense	9
Unrecognized Tax Benefits, Timing of Accrual For Interest On Nonperforming Assets	1,175
Unrecognized Tax Benefits, State Income Tax Exposure	$ 307