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Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($) | Sep. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024
--- | --- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Cash and due from banks | $ 237,466,000 | $ 259,996,000 | $ 296,188,000
FEDERAL FUNDS SOLD | 11,750,000 | 0 | 0
INTEREST-BEARING DEMAND DEPOSITS IN BANKS | 401,580,000 | 503,417,000 | 287,476,000
Available-for-sale securities | 5,260,813,000 | 4,617,759,000 | 4,612,299,000
Loans held-for-investment, net of allowance for credit losses | 8,137,667,000 | 7,814,773,000 | 7,623,255,000
Loans held for sale | 26,015,000 | 8,235,000 | 20,114,000
Borrowings | 21,956,000 | 135,603,000 | 25,978,000
IRLCs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
IRLCs | 726,000 | 238,000 | 499,000
Forward mortgage-backed securities trades asset (liability) | 0 | 0 | 0
Forward Mortgage-Backed Securities Trades [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
IRLCs | 0 | 84,000 | 0
Forward mortgage-backed securities trades asset (liability) | 214,000 | 0 | 98,000
Carrying Value [Member] | Level 1 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Cash and due from banks | 237,466,000 | 259,996,000 | 296,188,000
FEDERAL FUNDS SOLD | 11,750,000 | 0 | 0
INTEREST-BEARING DEMAND DEPOSITS IN BANKS | 401,580,000 | 503,417,000 | 287,476,000
Deposits with no stated maturities | 11,937,612,000 | 11,181,898,000 | 10,746,194,000
Carrying Value [Member] | Level 2 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Loans held for sale | 26,015,000 | 8,235,000 | 20,114,000
Accrued interest receivable | 62,138,000 | 60,749,000 | 56,427,000
Deposits with stated maturities | 908,636,000 | 917,276,000 | 1,009,667,000
Repurchase Agreements | 50,646,000 | 61,416,000 | 57,557,000
Borrowings | 21,956,000 | 135,603,000 | 25,978,000
Accrued interest payable | 6,059,000 | 6,909,000 | 9,502,000
Carrying Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Forward mortgage-backed securities trades asset (liability) | (214,000) | 84,000 | (98,000)
Carrying Value [Member] | Levels 1 and 2 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Available-for-sale securities | 5,260,813,000 | 4,617,759,000 | 4,612,299,000
Carrying Value [Member] | Level 3 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Loans held-for-investment, net of allowance for credit losses | 8,137,667,000 | 7,814,773,000 | 7,623,255,000
Carrying Value [Member] | Level 3 Inputs [Member] | IRLCs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
IRLCs | 726,000 | 238,000 | 499,000
Estimated Fair Value [Member] | Level 1 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Cash and due from banks | 237,466,000 | 259,996,000 | 296,188,000
FEDERAL FUNDS SOLD | 11,750,000 | 0 | 0
INTEREST-BEARING DEMAND DEPOSITS IN BANKS | 401,580,000 | 503,417,000 | 287,476,000
Deposits with no stated maturities | 11,937,612,000 | 11,181,898,000 | 10,746,194,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Loans held for sale | 26,102,000 | 8,276,000 | 20,293,000
Accrued interest receivable | 62,138,000 | 60,749,000 | 56,427,000
Deposits with stated maturities | 910,133,000 | 919,774,000 | 1,011,199,000
Repurchase Agreements | 50,646,000 | 61,416,000 | 57,557,000
Borrowings | 21,956,000 | 135,603,000 | 25,978,000
Accrued interest payable | 6,059,000 | 6,909,000 | 9,502,000
Estimated Fair Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Forward mortgage-backed securities trades asset (liability) | (214,000) | 84,000 | (98,000)
Estimated Fair Value [Member] | Levels 1 and 2 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Available-for-sale securities | 5,260,813,000 | 4,617,759,000 | 4,612,299,000
Estimated Fair Value [Member] | Level 3 Inputs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Loans held-for-investment, net of allowance for credit losses | 8,153,930,000 | 7,806,258,000 | 7,607,920,000
Estimated Fair Value [Member] | Level 3 Inputs [Member] | IRLCs [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
IRLCs | $ 726,000 | $ 238,000 | $ 499,000

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- Definition The amount outstanding of funds lent to other depository institutions, securities brokers, or securities dealers in the form of Federal Funds sold; for example, immediately available funds lent under agreements or contracts that mature in one business day or roll over under a continuing contract, regardless of the nature of the transaction or the collateral involved, excluding overnight lending for commercial and industrial purposes. Also include Federal Funds sold under agreements to resell on a gross basis, excluding (1) sales of term Federal Funds, (2) due bills representing purchases of securities or other assets by the reporting bank that have not yet been delivered and similar instruments, (3) resale agreements that mature in more than one business day involving assets other than securities, and (4) yield maintenance dollar repurchase agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(3)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
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