Loans - Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 22,432,419	$ 21,891,812
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	286,215	281,495
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,333,349	6,306,980
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	98,888	98,439	$ 94,307	$ 87,569
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,208,070	1,094,669
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	11,082	11,563	10,256	9,992
Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	4,159,240	3,987,913
Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	3,747,762	3,773,028
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,650,291	2,549,869
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	3,880,604	3,718,668
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	27,394	25,637	18,924	19,106
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	453,103	460,685
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	10,809	10,746	$ 8,824	$ 10,279
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	18,103	19,272
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	14,659	16,619
Specific Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	700	700
Specific Valuation Allowances [Member] | Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	722	722
Specific Valuation Allowances [Member] | Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	0	0
Specific Valuation Allowances [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	513	513
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	1,428	637
Specific Valuation Allowances [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	81	81
Loans Individually Evaluated for Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	67,930	66,907
Loans Individually Evaluated for Impairment [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	42,236	48,456
Loans Individually Evaluated for Impairment [Member] | Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,523	3,023
Loans Individually Evaluated for Impairment [Member] | Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	13,297	7,069
Loans Individually Evaluated for Impairment [Member] | Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	440	466
Loans Individually Evaluated for Impairment [Member] | Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,209	1,672
Loans Individually Evaluated for Impairment [Member] | Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	7,144	6,140
Loans Individually Evaluated for Impairment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 81	$ 81