Fair Value of Assets and Liabilities - Balances of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets:
Available-for-Sale: Fair Value	$ 3,955,476	$ 4,276,056
Loans Held for Sale	4,514	26,746
Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	65,841	75,818
Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,673	1,780
Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	384,319	383,113
Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	1,226,339	1,319,042
Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,849,867	2,090,326
Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	3,239,757	3,565,258
Fair Value, Measurements, Recurring
Assets:
Available-for-Sale: Fair Value	3,955,476	4,276,056
Loans Held for Sale	4,514	26,746
Mortgage Servicing Rights	747	800
Other Assets	46,929	56,411
Derivatives	22,494	42,011
Total Assets Measured at Fair Value on a Recurring Basis	4,030,160	4,402,024
Liabilities:
Derivatives	107,661	18,816
Total Liabilities Measured at Fair Value on a Recurring Basis	107,661	18,816
Fair Value, Measurements, Recurring \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	263,886	250,087
Fair Value, Measurements, Recurring \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	65,841	75,818
Fair Value, Measurements, Recurring \| Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,673	1,780
Fair Value, Measurements, Recurring \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	384,319	383,113
Fair Value, Measurements, Recurring \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	1,226,339	1,319,042
Fair Value, Measurements, Recurring \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,849,867	2,090,326
Fair Value, Measurements, Recurring \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	163,551	155,890
Fair Value, Measurements, Recurring \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	3,239,757	3,565,258
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
Assets:
Available-for-Sale: Fair Value	145,514	114,845
Loans Held for Sale	0	0
Mortgage Servicing Rights	0	0
Other Assets	46,929	56,411
Derivatives	0	0
Total Assets Measured at Fair Value on a Recurring Basis	192,443	171,256
Liabilities:
Derivatives	0	0
Total Liabilities Measured at Fair Value on a Recurring Basis	0	0
Fair Value, Measurements, Recurring \| 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	145,514	114,845
Fair Value, Measurements, Recurring \| 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 \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) \| Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring \| 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 \| 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 \| 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 \| 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 \| 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 \| Significant Other Observable Inputs (Level 2)
Assets:
Available-for-Sale: Fair Value	3,809,962	4,161,211
Loans Held for Sale	4,514	26,746
Mortgage Servicing Rights	0	0
Other Assets	0	0
Derivatives	76	194
Total Assets Measured at Fair Value on a Recurring Basis	3,814,552	4,188,151
Liabilities:
Derivatives	2,295	903
Total Liabilities Measured at Fair Value on a Recurring Basis	2,295	903
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	118,372	135,242
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	65,841	75,818
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,673	1,780
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	384,319	383,113
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	1,226,339	1,319,042
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,849,867	2,090,326
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	163,551	155,890
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	3,239,757	3,565,258
Fair Value, Measurements, Recurring \| Significant Other Unobservable Inputs (Level 3)
Assets:
Available-for-Sale: Fair Value	0	0
Loans Held for Sale	0	0
Mortgage Servicing Rights	747	800
Other Assets	0	0
Derivatives	22,418	41,817
Total Assets Measured at Fair Value on a Recurring Basis	23,165	42,617
Liabilities:
Derivatives	105,366	17,913
Total Liabilities Measured at Fair Value on a Recurring Basis	105,366	17,913
Fair Value, Measurements, Recurring \| 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 \| 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 \| Significant Other Unobservable Inputs (Level 3) \| Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring \| Significant Other Unobservable Inputs (Level 3) \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring \| Significant Other Unobservable Inputs (Level 3) \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring \| Significant Other Unobservable Inputs (Level 3) \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring \| Significant Other Unobservable Inputs (Level 3) \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	0	0
Fair Value, Measurements, Recurring \| Significant Other Unobservable Inputs (Level 3) \| Mortgage-Backed Securities
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 security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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 valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security.

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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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