Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($)	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 224,875,000	$ 293,286,000	$ 203,187,000
Interest-Bearing Deposits in Banks and Other Financial Institutions	221,336,000	37,392,000	394,566,000
Securities available-for-sale, Estimated Fair Value	5,298,557,000	5,474,359,000	6,502,495,000
Net loans held for -investment	6,495,397,000	6,366,034,000	5,499,256,000
Loans held for sale	11,996,000	11,965,000	27,670,000
Borrowings	632,927,000	642,507,000	758,595,000
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	827,000	400,000	276,000
Liability Derivative Fair Value	0	0	0
Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	0	85,000	2,103,000
Liability Derivative Fair Value	334,000	0	0
Carrying Value [Member] \| Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	224,875,000	293,286,000	203,187,000
Interest-Bearing Deposits in Banks and Other Financial Institutions	221,336,000	37,392,000	394,566,000
Deposits with no stated maturities	10,196,920,000	10,480,841,000	10,550,695,000
Carrying Value [Member] \| Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	11,996,000	11,965,000	27,670,000
Accrued interest receivable	50,658,000	58,162,000	48,066,000
Deposits with stated maturities	739,498,000	524,666,000	449,130,000
Borrowings	632,927,000	642,507,000	758,595,000
Accrued interest payable		1,121,000	268,000
Carrying Value [Member] \| Level 2 Inputs [Member] \| IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	827,000	400,000	276,000
Carrying Value [Member] \| Level 2 Inputs [Member] \| Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability Derivative Fair Value	(334,000)	85,000	2,103,000
Carrying Value [Member] \| Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Estimated Fair Value	5,298,557,000	5,474,359,000	6,502,495,000
Carrying Value [Member] \| Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans held for -investment	6,495,397,000	6,366,034,000	5,499,256,000
Estimated Fair Value [Member] \| Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	224,875,000	293,286,000	203,187,000
Interest-Bearing Deposits in Banks and Other Financial Institutions	221,336,000	37,392,000	394,566,000
Deposits with no stated maturities	10,196,920,000	10,480,841,000	10,550,695,000
Estimated Fair Value [Member] \| Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	12,018,000	11,965,000	26,985,000
Accrued interest receivable	50,658,000	58,162,000	48,066,000
Deposits with stated maturities	736,434,000	518,811,000	449,987,000
Borrowings	632,927,000	642,507,000	758,595,000
Accrued interest payable	3,617,000	1,121,000	268,000
Estimated Fair Value [Member] \| Level 2 Inputs [Member] \| IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	827,000	400,000	276,000
Estimated Fair Value [Member] \| Level 2 Inputs [Member] \| Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability Derivative Fair Value	(334,000)	85,000	2,103,000
Estimated Fair Value [Member] \| Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Estimated Fair Value	5,298,557,000	5,474,359,000	6,502,495,000
Estimated Fair Value [Member] \| Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans held for -investment	$ 6,464,027,000	$ 6,372,859,000	$ 5,522,778,000

Accrued interest payable.

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Deposits with no stated maturities.

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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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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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Fair value, before 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 elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, before 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 elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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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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