v3.25.2
Loans - Additional Information (Detail)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Dec. 31, 2024
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 280,800   280,800   295,800
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged 19,800,000   19,800,000   19,200,000
Federal Home Loan Bank Borrowings, Fair Value Disclosure 0   0   0
Loans, net of unearned discounts $ 21,254,495   $ 21,254,495   $ 20,754,813
Texas Leading Index economic condition indicator 126.1   126.1   125.3
Combination: Payment Delay and Term Extention          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts $ 0   $ 0    
Financing Receivables, 30 to 89 Days Past Due [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts $ 62,310   $ 62,310    
Automobile Loan [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Percentage of total loans 5.50%   5.50%    
Commercial and Industrial Total Energy Loans [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Percentage of total loans 6.20%   6.20%    
Loans, net of unearned discounts $ 1,315,227   $ 1,315,227   $ 1,128,895
Commercial and Industrial Total Energy Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 1,104   1,104    
Non Accrual Loans [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Financing Receivable, Excluding Accrued Interest, Impaired Interest Lost On Nonaccrual Loans 1,300 $ 1,300 2,700 $ 2,500  
Total consumer real estate loans [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 3,339,275   3,339,275   3,103,389
Total consumer real estate loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 19,316   19,316    
Commercial Portfolio Segment [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 6,069,215   6,069,215   6,109,532
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 0 $ 27,731 0 $ 27,731  
Commercial Portfolio Segment [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 26,553   26,553    
Consumer Loan [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 437,029   437,029   444,474
Consumer Loan [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 4,546   4,546    
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 7,600   7,600    
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year 3,800   3,800    
Commercial mortgage [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Loans, net of unearned discounts 7,472,048   7,472,048   7,165,220
Commitments to Extend Credit [Member] | Automobile Loan [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Unfunded balances 519,700   519,700    
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] | Automobile Loan [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Unfunded balances 20,000   20,000    
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Unfunded balances 67,300   67,300    
Loans Receivable [Member]          
Accounts, Notes, Loans and Financing Receivable [Line Items]          
Interest Receivable $ 88,800   $ 88,800   $ 86,800