v3.26.3
Borrowing Arrangements Narrative (Details)
 9 Months Ended
Sep. 30, 2026
USD ($)
oustanding_letters_of_credit
credit_line
Dec. 31, 2025
USD ($)
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) 1 year  
Securities sold under repurchase agreements $ 59,600,000 98,700,000
Federal Home Loan Bank borrowings, additional funding available 1,770,000,000  
Asset Pledged As Collateral, Excess Amount    
Line of Credit Facility [Line Items]    
Debt Securities 12,900,000 241,800,000
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 4  
Letters of Credit Outstanding, Amount $ 19,300,000  
Minimum    
Line of Credit Facility [Line Items]    
Federal Home Loan Bank borrowings interest rates 3.88%  
Federal Home Loan Bank borrowings maturities 1 day  
Maximum    
Line of Credit Facility [Line Items]    
Federal Home Loan Bank borrowings interest rates 5.28%  
Federal Home Loan Bank borrowings maturities 1 year 9 months 18 days  
Federal Reserve Discount Window    
Line of Credit Facility [Line Items]    
Other borrowings $ 835,000,000.0 $ 110,000,000.0