Loans - Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 22,975,658	$ 21,891,812
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,325,658	6,306,980
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	705,381	767,724
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	338,407	252,295
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	89,852	74,650
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
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
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	10,988,576	10,310,810
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,140,127	1,068,393
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,045,511	1,035,971
Home Improvement Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	862,240	874,148
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	886,975	594,825
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	135,129	145,331
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
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	15,058,558	14,029,478
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 457,802	$ 460,685