Loans - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($) Rate	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration of loans in a single industry in excess of ten percent	0.00%		0.00%
Maximum percentage loan related to single industry	10.00%		10.00%
U.S. dollar denominated loans and commitments to borrowers in Mexico	$ 0		$ 0			$ 0
Loans and Leases Receivable, Related Parties	$ 278,300		$ 278,300			$ 416,100
Financing Receivable Modified Prime Rate Spread at Time of Modification | Rate				1.75%
Financing Receivable Modified Interest Rate at Time of Modification | Rate				10.25%
Financing Receivable Modified Fixed Interest Rate After Rate Modification | Rate				6.74%
Texas Leading Index economic condition indicator	126.9		126.9			127.2
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)			$ 7,200
Financing Receivable, Allowance for Credit Loss	$ 263,129		263,129			$ 245,996
Loans, net of unearned discounts	20,054,863		20,054,863			18,824,251
Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	27,170		27,170
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	22,063		22,063
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	16,551		16,551
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	7,995		7,995
Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 46,925	$ 35,697	$ 46,925	$ 35,697
Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5.60%		5.60%
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loans	5.30%		5.30%
Financing Receivable, Allowance for Credit Loss	$ 12,121	17,066	$ 12,121	17,066	$ 11,485	17,814	$ 14,929	$ 18,062
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0	79	518
Loans, net of unearned discounts	1,069,718		1,069,718			936,737
Financing Receivable, Year One, Originated, Current Fiscal Year	329,675		329,675
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	26,287		26,287
Commercial and Industrial Total Energy Loans [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	4,086		4,086
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Commercial and Industrial Total Energy Loans [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	79		79
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	1,500	1,200	4,000	2,700
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	17,652	15,039	17,652	15,039	15,707	13,538	13,035	8,004
Financing Receivable, Allowance for Credit Loss, Writeoff	2,013	170	4,090	1,500
Loans, net of unearned discounts	2,922,877		2,922,877			2,460,726
Total consumer real estate loans [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0		0
Total consumer real estate loans [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	407		407
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	80,576	74,307	80,576	74,307	78,554	74,006	75,166	104,237
Financing Receivable, Allowance for Credit Loss, Writeoff	3,907	943	10,333	14,259
Loans, net of unearned discounts	5,822,976		5,822,976			5,967,182
Financing Receivable, Year One, Originated, Current Fiscal Year	1,213,266		1,213,266
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	645,575		645,575
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	22,756		22,756
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,822		2,822
Commercial Portfolio Segment [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	5		5
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,741		1,741
Commercial Portfolio Segment [Member] | Additional Funding Agreement Terms
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	52,000		52,000
Commercial Portfolio Segment [Member] | Combination: Payment Delay and Term Extention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	46,925	15,912	46,925	15,912
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)			923
Financing Receivable, Allowance for Credit Loss	9,955	9,331	9,955	9,331	$ 10,541	10,040	$ 9,563	$ 7,017
Financing Receivable, Allowance for Credit Loss, Writeoff	8,007	$ 8,189	24,624	$ 22,147
Loans, net of unearned discounts	458,772		458,772			476,962
Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	0		0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	374		374
Consumer Loan [Member] | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	16,546		16,546
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,768		5,768
Bank Overdrafts | Financial Asset, Other than Financial Asset Acquired with Credit Deterioration | Nonperforming Financial Instruments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	16,300		16,300
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,500		5,500
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Change in Method, Credit Loss Expense (Reversal)			6,200
Loans, net of unearned discounts	6,961,403		6,961,403			6,746,709
Commitments to Extend Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial instruments with off- balance-sheet risk	12,161,223		12,161,223			12,195,073
Commitments to Extend Credit [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	405,400		405,400
Commitments to Extend Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	1,100,000		1,100,000
Standby Letters of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial instruments with off- balance-sheet risk	433,399		433,399			438,635
Standby Letters of Credit [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	20,300		20,300
Standby Letters of Credit [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded balances	70,500		70,500
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 85,800		$ 85,800			$ 90,800