Loans - Financing Receivables, Modified Loans Past Due in Excess of 90 Days or on Non-Accrual Status at Period-End (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 18,399,259	$ 17,154,969
Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	35,697		$ 0
Combination: Payment Delay and Term Extention | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		0
Combination: Payment Delay and Term Extention | Charge-offs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		352
Combination: Payment Delay and Term Extention | Proceeds from sales
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		1,070
Extended Maturity and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	2,100		0
Extended Maturity and Interest Rate Reduction | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	2,100
Extended Maturity and Interest Rate Reduction | Charge-offs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0
Extended Maturity and Interest Rate Reduction | Proceeds from sales
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0
Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		1,083
Payment Deferral | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			1,083
Payment Deferral | Charge-offs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			371
Payment Deferral | Proceeds from sales
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			0
Commercial Real Estate Buildings Land And Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	7,193,785	6,706,078
Commercial Real Estate Buildings Land And Other Loans [Member] | Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	19,785		0
Commercial Real Estate Buildings Land And Other Loans [Member] | Combination: Payment Delay and Term Extention | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		0
Commercial Real Estate Buildings Land And Other Loans [Member] | Combination: Payment Delay and Term Extention | Charge-offs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		352
Commercial Real Estate Buildings Land And Other Loans [Member] | Combination: Payment Delay and Term Extention | Proceeds from sales
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		1,070
Commercial Real Estate Buildings Land And Other Loans [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	2,100		0
Commercial Real Estate Buildings Land And Other Loans [Member] | Extended Maturity and Interest Rate Reduction | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	2,100
Commercial Real Estate Buildings Land And Other Loans [Member] | Extended Maturity and Interest Rate Reduction | Charge-offs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0
Commercial Real Estate Buildings Land And Other Loans [Member] | Extended Maturity and Interest Rate Reduction | Proceeds from sales
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0
Commercial Real Estate Buildings Land And Other Loans [Member] | Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0		1,083
Commercial Real Estate Buildings Land And Other Loans [Member] | Payment Deferral | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			1,083
Commercial Real Estate Buildings Land And Other Loans [Member] | Payment Deferral | Charge-offs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			371
Commercial Real Estate Buildings Land And Other Loans [Member] | Payment Deferral | Proceeds from sales
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts			$ 0
Commercial and Industrial Total Energy Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	1,006,859	925,729
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	5,836,877	$ 5,674,798
Commercial Portfolio Segment [Member] | Combination: Payment Delay and Term Extention
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	15,912
Commercial Portfolio Segment [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	0
Commercial Portfolio Segment [Member] | Payment Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans, net of unearned discounts	$ 0