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Loans - Additional Information (Detail) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) Rate | Jun. 30, 2024 USD ($) | Dec. 31, 2023 USD ($) | Jun. 30, 2023 USD ($) | Dec. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Concentration of loans in a single industry in excess of ten percent | 0.00% |  | 0.00% |  |  |  |  |
Maximum percentage loan related to single industry | 10.00% |  | 10.00% |  |  |  |  |
U.S. dollar denominated loans and commitments to borrowers in Mexico | $ 0 |  | $ 0 |  |  | $ 0 |  |
Loans and Leases Receivable, Related Parties | $ 278,300 |  | $ 278,300 |  |  | $ 416,100 |  |
Financing Receivable Modified Prime Rate Spread at Time of Modification | Rate |  |  |  | 1.75% |  |  |  |
Financing Receivable Modified Interest Rate at Time of Modification | Rate |  |  |  | 10.25% |  |  |  |
Financing Receivable Modified Fixed Interest Rate After Rate Modification | Rate |  |  |  | 6.74% |  |  |  |
Texas Leading Index economic condition indicator | 126.9 |  | 126.9 |  |  | 127.2 |  |
Financing Receivable, Change in Method, Credit Loss Expense (Reversal) |  |  | $ 7,200 |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | $ 263,129 |  | 263,129 |  |  | $ 245,996 |  |
Loans, net of unearned discounts | 20,054,863 |  | 20,054,863 |  |  | 18,824,251 |  |
Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 27,170 |  | 27,170 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 22,063 |  | 22,063 |  |  |  |  |
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 16,551 |  | 16,551 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 7,995 |  | 7,995 |  |  |  |  |
Combination: Payment Delay and Term Extention |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned discounts | $ 46,925 | $ 35,697 | $ 46,925 | $ 35,697 |  |  |  |
Automobile Loan [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of total loans | 5.60% |  | 5.60% |  |  |  |  |
Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of total loans | 5.30% |  | 5.30% |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | $ 12,121 | 17,066 | $ 12,121 | 17,066 | $ 11,485 | 17,814 | $ 14,929 | $ 18,062
Financing Receivable, Allowance for Credit Loss, Writeoff | 0 | 0 | 79 | 518 |  |  |  |
Loans, net of unearned discounts | 1,069,718 |  | 1,069,718 |  |  | 936,737 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 329,675 |  | 329,675 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 26,287 |  | 26,287 |  |  |  |  |
Commercial and Industrial Total Energy Loans [Member] | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 4,086 |  | 4,086 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 0 |  | 0 |  |  |  |  |
Commercial and Industrial Total Energy Loans [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 0 |  | 0 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 79 |  | 79 |  |  |  |  |
Non Accrual Loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Additional interest that would have been recognized on non-accrual loans, net of tax | 1,500 | 1,200 | 4,000 | 2,700 |  |  |  |
Total consumer real estate loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 17,652 | 15,039 | 17,652 | 15,039 | 15,707 | 13,538 | 13,035 | 8,004
Financing Receivable, Allowance for Credit Loss, Writeoff | 2,013 | 170 | 4,090 | 1,500 |  |  |  |
Loans, net of unearned discounts | 2,922,877 |  | 2,922,877 |  |  | 2,460,726 |  |
Total consumer real estate loans [Member] | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 0 |  | 0 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 0 |  | 0 |  |  |  |  |
Total consumer real estate loans [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 0 |  | 0 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 407 |  | 407 |  |  |  |  |
Commercial Portfolio Segment [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 80,576 | 74,307 | 80,576 | 74,307 | 78,554 | 74,006 | 75,166 | 104,237
Financing Receivable, Allowance for Credit Loss, Writeoff | 3,907 | 943 | 10,333 | 14,259 |  |  |  |
Loans, net of unearned discounts | 5,822,976 |  | 5,822,976 |  |  | 5,967,182 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 1,213,266 |  | 1,213,266 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 645,575 |  | 645,575 |  |  |  |  |
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 22,756 |  | 22,756 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 2,822 |  | 2,822 |  |  |  |  |
Commercial Portfolio Segment [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 5 |  | 5 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 1,741 |  | 1,741 |  |  |  |  |
Commercial Portfolio Segment [Member] | Additional Funding Agreement Terms |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned discounts | 52,000 |  | 52,000 |  |  |  |  |
Commercial Portfolio Segment [Member] | Combination: Payment Delay and Term Extention |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned discounts | 46,925 | 15,912 | 46,925 | 15,912 |  |  |  |
Consumer Loan [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Change in Method, Credit Loss Expense (Reversal) |  |  | 923 |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 9,955 | 9,331 | 9,955 | 9,331 | $ 10,541 | 10,040 | $ 9,563 | $ 7,017
Financing Receivable, Allowance for Credit Loss, Writeoff | 8,007 | $ 8,189 | 24,624 | $ 22,147 |  |  |  |
Loans, net of unearned discounts | 458,772 |  | 458,772 |  |  | 476,962 |  |
Consumer Loan [Member] | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 0 |  | 0 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 374 |  | 374 |  |  |  |  |
Consumer Loan [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 16,546 |  | 16,546 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 5,768 |  | 5,768 |  |  |  |  |
Bank Overdrafts | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 16,300 |  | 16,300 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 5,500 |  | 5,500 |  |  |  |  |
Commercial mortgage [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Change in Method, Credit Loss Expense (Reversal) |  |  | 6,200 |  |  |  |  |
Loans, net of unearned discounts | 6,961,403 |  | 6,961,403 |  |  | 6,746,709 |  |
Commitments to Extend Credit [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financial instruments with off- balance-sheet risk | 12,161,223 |  | 12,161,223 |  |  | 12,195,073 |  |
Commitments to Extend Credit [Member] | Automobile Loan [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unfunded balances | 405,400 |  | 405,400 |  |  |  |  |
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unfunded balances | 1,100,000 |  | 1,100,000 |  |  |  |  |
Standby Letters of Credit [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financial instruments with off- balance-sheet risk | 433,399 |  | 433,399 |  |  | 438,635 |  |
Standby Letters of Credit [Member] | Automobile Loan [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unfunded balances | 20,300 |  | 20,300 |  |  |  |  |
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unfunded balances | 70,500 |  | 70,500 |  |  |  |  |
Loans Receivable [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Interest Receivable | $ 85,800 |  | $ 85,800 |  |  | $ 90,800 |  |

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