Loans (Age Analysis of Past Due Loans, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	$ 21,891,812	$ 20,754,813
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	21,671
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	6,306,980	6,109,532
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	4,273
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	1,094,669	1,128,895
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	3,987,913	3,622,201
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	3,465
Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,773,028	3,543,019
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	6,290
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,549,869	2,803,303
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	1,451
Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,718,668	3,103,389
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	5,680
Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	460,685	444,474
Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing	512
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	158,172
Financing Receivables, 30 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	32,776
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	19,480
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	17,351
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	49,305
Financing Receivables, 30 to 89 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	7,955
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	26,281	17,015
Financing Receivables, 30 to 89 Days Past Due [Member] | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	5,024	6,693
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	50,057
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	20,635
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	3,023
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	3,465
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	6,755
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	3,218
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	12,184	12,028
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	777	822
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	208,229
Financial Asset, Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	53,411
Financial Asset, Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	22,503
Financial Asset, Past Due | Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	20,816
Financial Asset, Past Due | Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	56,060
Financial Asset, Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	11,173
Financial Asset, Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	38,465	29,043
Financial Asset, Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	5,801	7,515
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	21,683,583
Financial Asset, Not Past Due | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	6,253,569
Financial Asset, Not Past Due | Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	1,072,166
Financial Asset, Not Past Due | Commercial Real Estate Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,967,097
Financial Asset, Not Past Due | Commercial Real Estate Non-Owner Occupied
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,716,968
Financial Asset, Not Past Due | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	2,538,696
Financial Asset, Not Past Due | Total consumer real estate loans [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	3,680,203	3,074,346
Financial Asset, Not Past Due | Consumer Loan [Member]
Financing Receivable, Past Due [Line Items]
Loans, net of unearned discounts	$ 454,884	$ 436,959