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Loans - Additional Information (Detail) $ in Thousands | 3 Months Ended | 6 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2024 USD ($) | Jun. 30, 2023 USD ($) | Jun. 30, 2024 USD ($) | Jun. 30, 2023 USD ($) | Mar. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Mar. 31, 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 | $ 281,000 |  | $ 281,000 |  |  | $ 416,100 |  |
Texas Leading Index economic condition indicator | 116.9 |  | 116.9 |  |  | 127.2 |  |
Financing Receivable, Change in Method, Credit Loss Expense (Reversal) |  |  | $ 7,200 |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | $ 256,307 |  | 256,307 |  |  | $ 245,996 |  |
Loans, net of unearned discounts | 19,995,756 |  | 19,995,756 |  |  | 18,824,251 |  |
Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 5,596 |  | 5,596 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 23,879 |  | 23,879 |  |  |  |  |
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 | 9,369 |  | 9,369 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | $ 6,263 |  | $ 6,263 |  |  |  |  |
Combination: Payment Delay and Term Extention |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned discounts |  | $ 36,486 |  | $ 36,486 |  |  |  |
Automobile Loan [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of total loans | 5.80% |  | 5.80% |  |  |  |  |
Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of total loans | 5.40% |  | 5.40% |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | $ 11,485 | 14,929 | $ 11,485 | 14,929 | $ 14,218 | 17,814 | $ 19,191 | $ 18,062
Financing Receivable, Allowance for Credit Loss, Writeoff | 79 | 518 | 79 | 518 |  |  |  |
Loans, net of unearned discounts | 1,096,657 |  | 1,096,657 |  |  | 936,737 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 304,570 |  | 304,570 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 36,014 |  | 36,014 |  |  |  |  |
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 | 4,522 |  | 4,522 |  |  |  |  |
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 | 1,300 | 835 | 2,500 | 1,400 |  |  |  |
Total consumer real estate loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 15,707 | 13,035 | 15,707 | 13,035 | 13,857 | 13,538 | 9,708 | 8,004
Financing Receivable, Allowance for Credit Loss, Writeoff | 408 | 1,080 | 2,077 | 1,330 |  |  |  |
Loans, net of unearned discounts | 2,740,728 |  | 2,740,728 |  |  | 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 | 0 |  | 0 |  |  |  |  |
Commercial Portfolio Segment [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 78,554 | 75,166 | 78,554 | 75,166 | 75,596 | 74,006 | 78,465 | 104,237
Financing Receivable, Allowance for Credit Loss, Writeoff | 4,282 | 7,136 | 6,426 | 13,316 |  |  |  |
Loans, net of unearned discounts | 6,210,179 |  | 6,210,179 |  |  | 5,967,182 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 1,208,188 |  | 1,208,188 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 719,078 |  | 719,078 |  |  |  |  |
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 746 |  | 746 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 3,764 |  | 3,764 |  |  |  |  |
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 | 0 |  | 0 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 471 |  | 471 |  |  |  |  |
Commercial Portfolio Segment [Member] | Additional Funding Agreement Terms |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned discounts | 0 |  | 0 |  |  |  |  |
Commercial Portfolio Segment [Member] | Combination: Payment Delay and Term Extention |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned discounts | 27,731 | 16,020 | 27,731 | 16,020 |  |  |  |
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 | 10,541 | 9,563 | 10,541 | 9,563 | $ 8,402 | 10,040 | $ 8,457 | $ 7,017
Financing Receivable, Allowance for Credit Loss, Writeoff | 8,360 | $ 7,016 | 16,617 | $ 13,958 |  |  |  |
Loans, net of unearned discounts | 452,980 |  | 452,980 |  |  | 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 | 0 |  | 0 |  |  |  |  |
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 | 9,369 |  | 9,369 |  |  |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 5,713 |  | 5,713 |  |  |  |  |
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 | 9,400 |  | 9,400 |  |  |  |  |
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 | 6,955,118 |  | 6,955,118 |  |  | 6,746,709 |  |
Commitments to Extend Credit [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financial instruments with off- balance-sheet risk | 11,908,533 |  | 11,908,533 |  |  | 12,195,073 |  |
Commitments to Extend Credit [Member] | Automobile Loan [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unfunded balances | 490,400 |  | 490,400 |  |  |  |  |
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unfunded balances | 1,000,000 |  | 1,000,000 |  |  |  |  |
Standby Letters of Credit [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financial instruments with off- balance-sheet risk | 404,673 |  | 404,673 |  |  | 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 | 65,800 |  | 65,800 |  |  |  |  |
Loans Receivable [Member] |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Interest Receivable | $ 96,200 |  | $ 96,200 |  |  | $ 90,800 |  |

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