Fair Value of Assets and Liabilities (Fair value on recurring basis) (Details 1) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Available-for-Sale: Fair Value	$ 2,279,722	$ 2,289,190
Loans Held for Sale	3,222	5,136
Fair Value, Measurements, Recurring [Member]
Assets:
Available-for-Sale: Fair Value	2,279,722	2,289,190
Loans Held for Sale	3,222	5,136
Mortgage Servicing Rights	2,072	2,604
Other Assets	19,548	18,794
Derivatives	16,800	16,515
Total Assets Measured at Fair Value on a Recurring Basis	2,321,364	2,332,239
Liabilites:
Derivatives	16,251	16,755
Total Liabilities Measured at Fair Value on a Recurring Basis	16,251	16,755
Fair Value, Measurements, Recurring [Member] \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	368,657	331,258
Fair Value, Measurements, Recurring [Member] \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	737,210	743,970
Fair Value, Measurements, Recurring [Member] \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	310,561	294,833
Fair Value, Measurements, Recurring [Member] \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	863,294	919,129
Fair Value, Measurements, Recurring [Member] \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	348,469	462,436
Fair Value, Measurements, Recurring [Member] \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	412,261	278,461
Fair Value, Measurements, Recurring [Member] \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	102,564	178,232
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
Assets:
Available-for-Sale: Fair Value	60,706	61,271
Loans Held for Sale	0	0
Mortgage Servicing Rights	0	0
Other Assets	19,548	18,794
Derivatives	0	0
Total Assets Measured at Fair Value on a Recurring Basis	80,254	80,065
Liabilites:
Derivatives	0	0
Total Liabilities Measured at Fair Value on a Recurring Basis	0	0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	60,706	61,271
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2)
Assets:
Available-for-Sale: Fair Value	2,219,016	2,227,919
Loans Held for Sale	3,222	5,136
Mortgage Servicing Rights	0	0
Other Assets	0	0
Derivatives	186	101
Total Assets Measured at Fair Value on a Recurring Basis	2,222,424	2,233,156
Liabilites:
Derivatives	39	459
Total Liabilities Measured at Fair Value on a Recurring Basis	39	459
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	307,951	269,987
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	737,210	743,970
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	310,561	294,833
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	863,294	919,129
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	348,469	462,436
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	412,261	278,461
Fair Value, Measurements, Recurring [Member] \| Significant Other Observable Inputs (Level 2) \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	102,564	178,232
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3)
Assets:
Available-for-Sale: Fair Value	0	0
Loans Held for Sale	0	0
Mortgage Servicing Rights	2,072	2,604
Other Assets	0	0
Derivatives	16,614	16,414
Total Assets Measured at Fair Value on a Recurring Basis	18,686	19,018
Liabilites:
Derivatives	16,212	16,296
Total Liabilities Measured at Fair Value on a Recurring Basis	16,212	16,296
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Significant Other Unobservable Inputs (Level 3) \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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Fair value portion of other assets.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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