Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total	$ 21,177,508	$ 20,279,547
Non- accrual	113,022	144,443
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	75,473	88,349
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	20,366	20,805
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	27,962	27,463
Current
Financing Receivable, Past Due [Line Items]
Total	20,940,685	19,998,487
Real estate - commercial mortgage
Financing Receivable, Past Due [Line Items]
Total	8,106,300	7,693,835
Non- accrual	42,749	70,161
Real estate - commercial mortgage \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	8,976	10,753
Real estate - commercial mortgage \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,819	4,644
Real estate - commercial mortgage \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,309	2,473
Real estate - commercial mortgage \| Current
Financing Receivable, Past Due [Line Items]
Total	8,051,447	7,605,804
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Total	4,577,334	4,473,004
Non- accrual	32,195	27,116
Commercial and Industrial \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	4,097	6,067
Commercial and Industrial \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,921	2,289
Commercial and Industrial \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,170	1,172
Commercial and Industrial \| Current
Financing Receivable, Past Due [Line Items]
Total	4,536,951	4,436,360
Real estate – residential mortgage
Financing Receivable, Past Due [Line Items]
Total	5,279,681	4,737,279
Non- accrual	21,154	26,294
Real estate – residential mortgage \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	44,563	57,061
Real estate – residential mortgage \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	10,146	8,209
Real estate – residential mortgage \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	19,406	20,215
Real estate – residential mortgage \| Current
Financing Receivable, Past Due [Line Items]
Total	5,184,412	4,625,500
Real estate - home equity
Financing Receivable, Past Due [Line Items]
Total	1,045,438	1,102,838
Non- accrual	5,532	6,105
Real estate - home equity \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,288	5,666
Real estate - home equity \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	3,544	2,444
Real estate - home equity \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	4,909	2,704
Real estate - home equity \| Current
Financing Receivable, Past Due [Line Items]
Total	1,025,165	1,085,919
Real-estate - construction
Financing Receivable, Past Due [Line Items]
Total	1,078,263	1,269,925
Non- accrual	677	1,368
Real-estate - construction \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,681	1,762
Real-estate - construction \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	330	1,758
Real-estate - construction \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Real-estate - construction \| Current
Financing Receivable, Past Due [Line Items]
Total	1,074,575	1,265,037
Consumer
Financing Receivable, Past Due [Line Items]
Total	743,976	699,179
Non- accrual	15	92
Consumer \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	8,511	6,692
Consumer \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,458	1,339
Consumer \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,124	899
Consumer \| Current
Financing Receivable, Past Due [Line Items]
Total	732,868	690,157
Leases and other loans
Financing Receivable, Past Due [Line Items]
Total	346,516	303,487
Non- accrual	10,700	13,307
Leases and other loans \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	357	348
Leases and other loans \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	148	122
Leases and other loans \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	44	0
Leases and other loans \| Current
Financing Receivable, Past Due [Line Items]
Total	335,267	289,710
US Government Insured Loan Program \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	100	100
US Government Insured Loan Program \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	100	700
US Government Insured Loan Program \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	$ 1,200	$ 7,700