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Loans (Narrative) (Detail) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 USD ($) Grade Rate | Dec. 31, 2022 USD ($) Grade | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
U.S. dollar denominated loans and commitments to borrowers in Mexico | $ 0 | $ 0 |  |
Commercial and industrial loans related to overdraft for correspondent bank customer | $ 13,400 | 10,300 |  |
Financing Receivable, Threshold Period Past Due | 90 days |  |  |
Loans, net of unearned discounts | $ 18,824,251 | $ 17,154,969 |  |
Loans Receivable, Basis Spread on Variable Rate | Rate | 1.75% |  |  |
Loan Receivable Variable Rate | Rate | 10.25% |  |  |
Loan Receivable Fixed Rate | Rate | 6.74% |  |  |
Number of days past due for payment of interest on loans, minimum | 120 days |  |  |
Texas Leading Index economic condition indicator | 126.8 | 130.4 |  |
Financing Receivable, Change in Method, Credit Loss Expense (Reversal) | $ (45,000) |  |  |
Financing Receivable, Allowance for Credit Loss | 245,996 | $ 227,621 |  |
Additional Funding Agreement Terms |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | 0 |  |  |
Nonperforming Financial Instruments [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 25,974 | 6,301 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 359 | 1,510 |  |
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 | 24,302 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 6,537 |  |  |
Loans Receivable [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Accrued interest receivable | $ 90,800 | 68,700 |  |
Commercial and Industrial Total Energy Loans [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Percentage of total loans | 5.00% |  |  |
Loans, net of unearned discounts | $ 935,265 | $ 925,729 |  |
Weighted Average Risk Grade | Grade | 6.05 | 5.67 |  |
Financing Receivable, Allowance for Credit Loss | $ 17,814 | $ 18,062 | $ 17,217 | $ 39,553
Financing Receivable, Year One, Originated, Current Fiscal Year | 277,722 | 352,224 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 61,500 | 100,862 |  |
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 | 5,875 | 4,657 |  |
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 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 0 |  |  |
Commercial and Industrial Total Energy Loans [Member] | Risk Grade One To Eight [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 869,749 | $ 887,182 |  |
Weighted Average Risk Grade | Grade | 5.73 | 5.44 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | $ 270,710 | $ 338,050 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 54,185 | 99,089 |  |
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 | $ 4,000 | 1,700 | 1,800 |
Grade 12 [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
General percentage of valuation allowance in excess of principal balance, maximum | 30.00% |  |  |
Grade 13 [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
General percentage of valuation allowance in excess of principal balance, minimum | 30.00% |  |  |
Commercial Portfolio Segment [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 5,959,133 | $ 5,674,798 |  |
Weighted Average Risk Grade | Grade | 6.60 | 6.39 |  |
Financing Receivable, Allowance for Credit Loss | $ 74,006 | $ 104,237 | 72,091 | 73,843
Financing Receivable, Year One, Originated, Current Fiscal Year | 1,619,306 | 1,703,185 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 768,246 | 657,039 |  |
Commercial Portfolio Segment [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 | 359 | 1,252 |  |
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 | 124 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 1,704 |  |  |
Commercial Portfolio Segment [Member] | Risk Grade One To Eight [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 5,499,829 | $ 5,435,917 |  |
Weighted Average Risk Grade | Grade | 6.32 | 6.24 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | $ 1,489,026 | $ 1,667,274 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | $ 706,210 | 618,756 |  |
Commercial and Industrial, Other Commercial [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Number of days past due for payment of interest on loans, minimum | 180 days |  |  |
Commercial Real Estate Portfolio Segment [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 8,982,644 | $ 8,183,325 |  |
Weighted Average Risk Grade | Grade | 7.24 | 7.10 |  |
Financing Receivable, Allowance for Credit Loss | $ 130,598 | $ 90,301 | 144,936 | 134,892
Financing Receivable, Year One, Originated, Current Fiscal Year | 2,205,943 | 2,567,912 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 2,361,998 | 2,019,736 |  |
Commercial Real Estate Buildings Land And Other Financing Receivable [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 7,301,920 | $ 6,706,078 |  |
Weighted Average Risk Grade | Grade | 7.20 | 7.09 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | $ 1,645,223 | $ 1,901,888 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 1,785,624 | 1,528,173 |  |
Commercial Real Estate Buildings Land And Other Financing Receivable [Member] | Nonperforming Financial Instruments [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | 20,099 | 1,644 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 0 | 0 |  |
Commercial Real Estate Buildings Land And Other Financing Receivable [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 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 6 |  |  |
Commercial Real Estate Buildings Land And Other Financing Receivable [Member] | Risk Grade One To Eight [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 6,895,358 | $ 6,340,028 |  |
Weighted Average Risk Grade | Grade | 7.03 | 6.94 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | $ 1,601,175 | $ 1,811,069 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 1,667,750 | 1,484,811 |  |
Construction Loans [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 1,680,724 | $ 1,477,247 |  |
Weighted Average Risk Grade | Grade | 7.45 | 7.12 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | $ 560,720 | $ 666,024 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 576,374 | 491,563 |  |
Construction 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 |  |
Construction 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 | 739 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 0 |  |  |
Construction Loans [Member] | Risk Grade One To Eight [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | $ 1,526,086 | $ 1,430,012 |  |
Weighted Average Risk Grade | Grade | 7.27 | 7.04 |  |
Financing Receivable, Year One, Originated, Current Fiscal Year | $ 538,072 | $ 640,948 |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 537,705 | 489,391 |  |
Consumer Loan [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | 476,962 | 492,726 |  |
Financing Receivable, Allowance for Credit Loss | 10,040 | 7,017 | 7,837 | $ 6,963
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 | 23,321 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | 4,546 |  |  |
Paycheck Protection Program [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans, net of unearned discounts | 9,521 | 34,852 |  |
Financing Receivable, Allowance for Credit Loss | 0 | $ 0 | $ 0 |
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 | 23,100 |  |  |
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year | $ 4,200 |  |  |
Automobile Loan |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Percentage of total loans | 5.90% |  |  |
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 |  |  |
Commitments to Extend Credit [Member] | Automobile Loan |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Unfunded balances | 522,800 |  |  |
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Unfunded balances | 86,900 |  |  |
Standby Letters of Credit [Member] | Automobile Loan |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Unfunded balances | $ 19,300 |  |  |

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- Definition Carrying value as of the balance sheet date of payments made in excess of existing cash balances, which will be honored by the bank but reflected as a loan to the entity. Overdrafts generally have a very short time frame for correction or repayment and are therefore more similar to short-term bank financing than trade financing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 45 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481573/470-10-45-10 + Details
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- Definition Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 310 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481746/310-40-50-1 + Details
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- Definition Amount before allowance and after 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481990/310-10-45-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-4 + Details
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