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Fair Value of Assets and Liabilities - Balances of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assets:
Available-for-Sale: Fair Value	$ 4,276,056	$ 3,791,689	$ 2,619,003
Loans Held for Sale	26,746	82,565
Derivatives	42,011	96,167
Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	75,818	24,840	55,097
Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,780	1,062	22,147
Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	383,113	224,605	336,321
Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	1,319,042	1,594,815	1,172,826
Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	2,090,326	1,518,283	586,761
Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	155,890	253,839	224,720
Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	3,565,258	3,366,937	$ 1,984,307
Fair Value, Measurements, Recurring
Assets:
Available-for-Sale: Fair Value	4,276,056	3,791,689
Loans Held for Sale	26,746	82,565
Mortgage Servicing Rights	800	958
Other Assets	56,411	53,410
Derivatives	42,011	96,167
Total Assets Measured at Fair Value on a Recurring Basis	4,402,024	4,024,789
Liabilities:
Derivatives	18,816	18,161
Total Liabilities Measured at Fair Value on a Recurring Basis	18,816	18,161
Fair Value, Measurements, Recurring \| Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets:
Available-for-Sale: Fair Value	250,087	174,245
Fair Value, Measurements, Recurring \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	75,818	24,840
Fair Value, Measurements, Recurring \| Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,780	1,062
Fair Value, Measurements, Recurring \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	383,113	224,605
Fair Value, Measurements, Recurring \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	1,319,042	1,594,815
Fair Value, Measurements, Recurring \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	2,090,326	1,518,283
Fair Value, Measurements, Recurring \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	155,890	253,839
Fair Value, Measurements, Recurring \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	3,565,258	3,366,937
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
Assets:
Available-for-Sale: Fair Value	114,845	921
Loans Held for Sale	0	0
Mortgage Servicing Rights	0	0
Other Assets	56,411	53,410
Derivatives	0	0
Total Assets Measured at Fair Value on a Recurring Basis	171,256	54,331
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	114,845	921
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	4,161,211	3,790,768
Loans Held for Sale	26,746	82,565
Mortgage Servicing Rights	0	0
Other Assets	0	0
Derivatives	194	878
Total Assets Measured at Fair Value on a Recurring Basis	4,188,151	3,874,211
Liabilities:
Derivatives	903	752
Total Liabilities Measured at Fair Value on a Recurring Basis	903	752
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	135,242	173,324
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by States and Political Subdivisions
Assets:
Available-for-Sale: Fair Value	75,818	24,840
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	1,780	1,062
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Debt Securities Issued by Corporations
Assets:
Available-for-Sale: Fair Value	383,113	224,605
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Residential - Government Agencies
Assets:
Available-for-Sale: Fair Value	1,319,042	1,594,815
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Residential - U.S. Government-Sponsored Enterprises
Assets:
Available-for-Sale: Fair Value	2,090,326	1,518,283
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Commercial - Government Agencies
Assets:
Available-for-Sale: Fair Value	155,890	253,839
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Mortgage-Backed Securities
Assets:
Available-for-Sale: Fair Value	3,565,258	3,366,937
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	800	958
Other Assets	0	0
Derivatives	41,817	95,289
Total Assets Measured at Fair Value on a Recurring Basis	42,617	96,247
Liabilities:
Derivatives	17,913	17,409
Total Liabilities Measured at Fair Value on a Recurring Basis	17,913	17,409
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