Federal Income Taxes (Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Tax Assets, Gross [Abstract]
Allowance for loan losses	$ 29,572	$ 30,916
Acquisition-related fair value adjustments	9,498	13,373
Accrued expenses not currently deductible	4,518	3,924
Other real estate	3,244	3,407
Nonaccrual loan interest	2,564	1,495
Employee benefit plans	2,451	7,875
Share-based awards	1,783	1,452
Other	1,714	1,096
Total deferred tax assets	55,344	63,538
Deferred Tax Liabilities, Gross [Abstract]
Goodwill	4,177	3,800
Loan fees	2,511	2,191
Investment securities available-for-sale	2,301	1,796
Core deposit intangible assets	1,202	1,468
Mortgage servicing rights	1,217	1,257
Prepaid expenses	941	888
Other	1,167	1,366
Total deferred tax liabilities, gross	13,516	12,766
Net deferred tax assets	$ 41,828	$ 50,772