Loans - Age Analysis of Past Due Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	$ 22,432,419	$ 21,891,812
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	15,890
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	6,333,349	6,306,980
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	4,423
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	1,208,070	1,094,669
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	0
Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	4,159,240	3,987,913
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	3,382
Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,747,762	3,773,028
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	1,654
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,650,291	2,549,869
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	0
Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,880,604	3,718,668
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	6,123
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	453,103	$ 460,685
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	308
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	127,559
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	23,366
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	1,443
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	15,553
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	4,662
Financing Receivables, 30 to 89 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	47,321
Financing Receivables, 30 to 89 Days Past Due [Member] | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	28,600
Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	6,614
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	48,427
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	18,877
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,523
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	8,233
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,094
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,304
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	13,828
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	568
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	175,986
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	42,243
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,966
Financial Asset, Past Due | Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	23,786
Financial Asset, Past Due | Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	6,756
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	49,625
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	42,428
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	7,182
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	22,256,433
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	6,291,106
Financial Asset, Not Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	1,204,104
Financial Asset, Not Past Due | Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	4,135,454
Financial Asset, Not Past Due | Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,741,006
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,600,666
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,838,176
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	$ 445,921