Loans - Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology (Detail) - USD ($)
$ in Thousands

Loans - Investment in Loans Related to Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology (Detail) - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 22,975,658		$ 21,891,812
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	283,712		281,495
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,325,658		6,306,980
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	91,420	$ 98,888	98,439	$ 95,484	$ 94,307	$ 87,569
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,133,640		1,094,669
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	9,407	11,082	11,563	10,389	10,256	9,992
Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	4,297,680		3,987,913
Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	3,970,141		3,773,028
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,720,755		2,549,869
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	4,069,982		3,718,668
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	29,146	27,394	25,637	21,707	18,924	19,106
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	457,802		460,685
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	11,234	$ 10,809	10,746	$ 9,300	$ 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	12,529		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	7,685		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	1,913		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	105,434		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	20,876		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	13,688		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	4,091		466
Loans Individually Evaluated for Impairment [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	56,054		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	8,121		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