Federal Income Taxes (Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets, Gross [Abstract]
Allowance for loan losses	$ 26,489	$ 27,675
Acquisition-related fair value adjustments	19,457	8,699
Accrued expenses not currently deductible	7,819	6,288
Nonaccrual loan interest	4,682	2,884
Other	12,729us-gaap_DeferredTaxAssetsOther	8,779us-gaap_DeferredTaxAssetsOther
Total deferred tax assets	71,176us-gaap_DeferredTaxAssetsGross	54,325us-gaap_DeferredTaxAssetsGross
Deferred Tax Liabilities, Gross [Abstract]
Defined benefit pension plan	565	8,020
Goodwill	5,205	4,680
Mortgage servicing rights	4,276	1,197
Core deposit intangible assets	5,072	932
Other	3,319us-gaap_DeferredTaxLiabilitiesOther	4,011us-gaap_DeferredTaxLiabilitiesOther
Total deferred tax liabilities	18,437us-gaap_DeferredIncomeTaxLiabilities	18,840us-gaap_DeferredIncomeTaxLiabilities
Net deferred tax assets	$ 52,739us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 35,485us-gaap_DeferredTaxAssetsLiabilitiesNet

Deferred Tax Assets, Acquisition Related Fair Value Adjustments

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Deferred Tax Assets, Nonaccrual Loan Interest

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Amount of deferred tax liability attributable to taxable temporary differences.

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Deferred Tax Liability

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from pension benefits.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued liabilities.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the provision for loan losses.

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Amount of deferred tax liability attributable to taxable temporary differences from goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences from intangible assets other than goodwill.

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Amount of deferred tax liability attributable to taxable temporary differences from mortgage servicing rights.

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Amount of deferred tax liability attributable to taxable temporary differences not separately disclosed.

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