Loans - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of loans in a single industry in excess of ten percent	0.00%
Maximum percentage loan related to single industry	10.00%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0		$ 0
Loans and Leases Receivable, Related Parties	$ 394,200		$ 391,300
Financing Receivable, Modifications, Number of Contracts	0	0
Texas Leading Index economic condition indicator	130.7		130.0
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)	$ (45,000)
Financing Receivable, Allowance for Credit Loss	231,514		$ 227,621
Financing Receivable, Allowance for Credit Loss, Writeoff	$ 4,200
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total energy loans to total loans	6.10%
Financing Receivable, Allowance for Credit Loss	$ 19,191	$ 15,422	18,062	$ 17,217
Financing Receivable, Allowance for Credit Loss, Writeoff	0	371
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	0	0	0
Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additional interest that would have been recognized on non-accrual loans, net of tax	600	$ 407
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	1,000,000
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	99,100
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 69,600		$ 68,700