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Borrowing Arrangements Narrative (Details)
 9 Months Ended
Sep. 30, 2025
USD ($)
credit_line
oustanding_letters_of_credit
Dec. 31, 2024
USD ($)
Line of Credit Facility [Line Items]    
Number of credit lines maintained by the Company | credit_line 3  
Federal funds purchased $ 0 $ 0
Maturity of repurchase agreements (less than) 2 years  
Securities sold under repurchase agreements $ 99,400,000 76,400,000
Federal Home Loan Bank borrowings, additional funding available 2,300,000,000  
Asset Pledged As Collateral, Excess Amount    
Line of Credit Facility [Line Items]    
Debt Securities 382,200,000 431,700,000
Frost Bank    
Line of Credit Facility [Line Items]    
Line of credit, maximum borrowing capacity 40,000,000.0  
Line of credit, capacity available for issuance of letters of credit $ 5,000,000.0  
Number of outstanding letters of credit | oustanding_letters_of_credit 1  
Letters of Credit Outstanding, Amount $ 155,000  
TIB - The Independent Bankers Bank    
Line of Credit Facility [Line Items]    
Line of credit, maximum borrowing capacity 15,000,000.0  
Amegy Bank    
Line of Credit Facility [Line Items]    
Line of credit, maximum borrowing capacity $ 25,000,000.0  
FHLB    
Line of Credit Facility [Line Items]    
Number of outstanding letters of credit | oustanding_letters_of_credit 2  
Letters of Credit Outstanding, Amount $ 6,200,000  
Minimum    
Line of Credit Facility [Line Items]    
Federal Home Loan Bank borrowings interest rates 0.31%  
Federal Home Loan Bank borrowings maturities 6 days  
Maximum    
Line of Credit Facility [Line Items]    
Federal Home Loan Bank borrowings interest rates 4.80%  
Federal Home Loan Bank borrowings maturities 2 years 9 months 18 days  
Federal Reserve Discount Window    
Line of Credit Facility [Line Items]    
Other borrowings $ 0 $ 0