Borrowing Arrangements Narrative (Details)	6 Months Ended
	Jun. 30, 2023 USD ($) credit_line oustanding_letters_of_credit	Dec. 31, 2022 USD ($)
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)	3 years
Securities sold under repurchase agreements	$ 104,200,000	33,200,000
Federal Home Loan Bank borrowings, additional funding available	1,800,000,000
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	593,600,000
Federal Reserve Bank Term Funding Program
Line of Credit Facility [Line Items]
Additional funding available	$ 708,000
Minimum
Line of Credit Facility [Line Items]
Federal Home Loan Bank borrowings interest rates	3.73%
Federal Home Loan Bank borrowings maturities	20 days
Maximum
Line of Credit Facility [Line Items]
Federal Home Loan Bank borrowings interest rates	5.53%
Federal Home Loan Bank borrowings maturities	5 years
Federal Reserve Discount Window
Line of Credit Facility [Line Items]
Other borrowings	$ 100,000,000	$ 188,000,000
Federal Reserve Bank Term Funding Program
Line of Credit Facility [Line Items]
Other borrowings	$ 296,200,000