Fair Value Measurement and Fair Value of Financial Instruments- Carrying Values and Fair Values of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financial Assets:
Amortized Cost	$ 94,278	$ 90,766
Investment securities held to maturity, fair value	96,174	93,868
Federal Home Loan Bank and other membership bank stocks, Carrying Value	9,210	11,979
Federal Home Loan Bank and other membership bank stocks, Fair Value	9,210	11,979
Loans	5,928,443	5,950,108
Fair Value	5,934,005	5,939,413
Financial Liabilities:
Certificates of deposit, Carrying Value	832,439	1,078,256
Certificates of deposit, Fair Value	828,779	1,077,620
Other borrowings, Carrying Value	25,000	25,000
Other borrowings, Fair Value	24,928	25,206
Subordinated debt, Carrying Value	113,045	118,257
Subordinated debentures, Fair Value	110,902	118,208
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets:
Investment securities held to maturity, 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
Other borrowings, Fair Value	0	0
Subordinated debentures, Fair Value	0	0
Significant Other Observable Inputs (Level 2)
Financial Assets:
Investment securities held to maturity, fair value	95,755	93,868
Federal Home Loan Bank and other membership bank stocks, Fair Value	9,210	11,979
Fair Value	0	0
Financial Liabilities:
Certificates of deposit, Fair Value	828,779	1,077,620
Other borrowings, Fair Value	24,928	25,206
Subordinated debentures, Fair Value	0	0
Significant Unobservable Inputs (Level 3)
Financial Assets:
Investment securities held to maturity, fair value	419	0
Federal Home Loan Bank and other membership bank stocks, Fair Value	0	0
Fair Value	5,934,005	5,939,413
Financial Liabilities:
Certificates of deposit, Fair Value	0	0
Other borrowings, Fair Value	0	0
Subordinated debentures, Fair Value	$ 110,902	$ 118,208

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Other Borrowings Fair Value Disclosure

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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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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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Amount excluding accrued interest, after allowance for credit loss, of financing receivable.

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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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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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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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