Loans - Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 19,995,756	$ 18,824,251
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,210,179	5,967,182
Energy Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	858,990	681,568
Energy Service [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	209,658	194,126
Energy Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	28,009	61,043
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,096,657	936,737
Commercial mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	6,955,118	6,746,709
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	1,997,545	1,680,724
Commercial land loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	542,549	555,211
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	9,495,212	8,982,644
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	832,307	792,876
Home Equity Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	790,727	694,966
Home Improvement Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	813,799	765,887
Other consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	303,895	206,997
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	2,740,728	2,460,726
Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	12,235,940	11,443,370
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned discounts	$ 452,980	$ 476,962