Borrowing Arrangements Narrative (Details)	9 Months Ended
	Sep. 30, 2022 USD ($) oustanding_letters_of_credit credit_line	Dec. 31, 2021 USD ($)
Line of Credit Facility [Line Items]
Number of credit lines maintained by the Company | credit_line	3
Federal funds purchased	$ 0	$ 0
Letters of Credit, Federal Home Loan Bank, as collateral	$ 0
Maturity of repurchase agreements (less than)	1 year 4 months 24 days
Securities sold under repurchase agreements	$ 40,700,000	23,200,000
Federal Home Loan Bank borrowings, additional funding available	1,620,000,000
Frost Bank
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	40,000,000
Line of credit, capacity available for issuance of letters of credit	$ 5,000,000
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
Comerica Bank
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	7,500,000
Federal Reserve Discount Window
Line of Credit Facility [Line Items]
Additional funding available	$ 505,800,000
Minimum
Line of Credit Facility [Line Items]
Federal Home Loan Bank borrowings interest rates	2.73%
Federal Home Loan Bank borrowings maturities	6 days
Maximum
Line of Credit Facility [Line Items]
Federal Home Loan Bank borrowings interest rates	4.799%
Federal Home Loan Bank borrowings maturities	5 years 9 months 18 days
Federal Reserve Discount Window
Line of Credit Facility [Line Items]
Other borrowings	$ 34,000,000	$ 0