Fair Value Measurement and Fair Value of Financial Instruments- Carrying Values and Fair Values of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Financial Assets:
Carrying Value	$ 827,107	$ 836,377
Fair Value	681,857	702,563
Federal Home Loan Bank and other membership bank stocks, Carrying Value	52,205	52,517
Federal Home Loan Bank and other membership bank stocks, Fair Value	52,205	52,517
Loans	8,243,601	8,266,698
Fair Value	7,730,750	7,714,736
Financial Liabilities:
Certificates of deposit, Carrying Value	2,030,771	1,967,448
Certificates of deposit, Fair Value	2,015,847	1,953,446
Long-term FHLB advances, Carrying Value	325,000	325,000
Long-term FHLB advances, Fair Value	329,757	333,878
Subordinated debt, Carrying Value	194,814	194,705
Subordinated debentures, Fair Value	151,092	149,063
U.S. government agencies
Financial Assets:
Carrying Value	10,270	10,406
Fair Value	9,777	9,914
Mortgage-backed securities, residential
Financial Assets:
Carrying Value	326,731	332,509
Fair Value	268,847	280,426
Collateralized mortgage obligations, residential
Financial Assets:
Carrying Value	12,079	12,243
Fair Value	9,201	9,447
Mortgage-backed securities, multifamily
Financial Assets:
Carrying Value	4,126	4,145
Fair Value	3,449	3,494
Obligations of states and political subdivisions
Financial Assets:
Carrying Value	471,022	474,195
Fair Value	388,527	396,859
Corporate bonds
Financial Assets:
Carrying Value	2,879	2,879
Fair Value	2,056	2,423
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets:
Fair Value	0	0
Federal Home Loan Bank and other membership bank stocks, Fair Value	0	0
Fair Value	0	0
Financial Liabilities:
Certificates of deposit, Fair Value	0	0
Long-term FHLB advances, Fair Value	0	0
Subordinated debentures, Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. government agencies
Financial Assets:
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Mortgage-backed securities, residential
Financial Assets:
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Collateralized mortgage obligations, residential
Financial Assets:
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Mortgage-backed securities, multifamily
Financial Assets:
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Obligations of states and political subdivisions
Financial Assets:
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate bonds
Financial Assets:
Fair Value	0	0
Significant Other Observable Inputs (Level 2)
Financial Assets:
Fair Value	681,857	702,563
Federal Home Loan Bank and other membership bank stocks, Fair Value	52,205	52,517
Fair Value	0	0
Financial Liabilities:
Certificates of deposit, Fair Value	2,015,847	1,953,446
Long-term FHLB advances, Fair Value	329,757	333,878
Subordinated debentures, Fair Value	0	0
Significant Other Observable Inputs (Level 2) \| U.S. government agencies
Financial Assets:
Fair Value	9,777	9,914
Significant Other Observable Inputs (Level 2) \| Mortgage-backed securities, residential
Financial Assets:
Fair Value	268,847	280,426
Significant Other Observable Inputs (Level 2) \| Collateralized mortgage obligations, residential
Financial Assets:
Fair Value	9,201	9,447
Significant Other Observable Inputs (Level 2) \| Mortgage-backed securities, multifamily
Financial Assets:
Fair Value	3,449	3,494
Significant Other Observable Inputs (Level 2) \| Obligations of states and political subdivisions
Financial Assets:
Fair Value	388,527	396,859
Significant Other Observable Inputs (Level 2) \| Corporate bonds
Financial Assets:
Fair Value	2,056	2,423
Significant Unobservable Inputs (Level 3)
Financial Assets:
Fair Value	0	0
Federal Home Loan Bank and other membership bank stocks, Fair Value	0	0
Fair Value	7,730,750	7,714,736
Financial Liabilities:
Certificates of deposit, Fair Value	0	0
Long-term FHLB advances, Fair Value	0	0
Subordinated debentures, Fair Value	151,092	149,063
Significant Unobservable Inputs (Level 3) \| U.S. government agencies
Financial Assets:
Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Mortgage-backed securities, residential
Financial Assets:
Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Collateralized mortgage obligations, residential
Financial Assets:
Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Mortgage-backed securities, multifamily
Financial Assets:
Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Obligations of states and political subdivisions
Financial Assets:
Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Corporate bonds
Financial Assets:
Fair Value	$ 0	$ 0

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Amount excluding accrued interest, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable. Excludes net investment in lease.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Amount of time deposit liabilities, including certificates of deposit.

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