Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total	$ 21,044,685	$ 20,279,547
Non- accrual	123,280	144,443
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	60,092	88,349
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	13,989	20,805
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	24,415	27,463
Current
Financing Receivable, Past Due [Line Items]
Total	20,822,909	19,998,487
Real estate - commercial mortgage
Financing Receivable, Past Due [Line Items]
Total	7,846,861	7,693,835
Non- accrual	53,815	70,161
Real estate - commercial mortgage | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,566	10,753
Real estate - commercial mortgage | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,671	4,644
Real estate - commercial mortgage | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,233	2,473
Real estate - commercial mortgage | Current
Financing Receivable, Past Due [Line Items]
Total	7,782,576	7,605,804
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Total	4,602,446	4,477,537
Non- accrual	29,488	27,116
Commercial and Industrial | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	3,542	6,067
Commercial and Industrial | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,977	2,289
Commercial and Industrial | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,100	1,172
Commercial and Industrial | Current
Financing Receivable, Past Due [Line Items]
Total	4,566,339	4,440,893
Real estate – residential mortgage
Financing Receivable, Past Due [Line Items]
Total	5,147,262	4,737,279
Non- accrual	21,700	26,294
Real estate – residential mortgage | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	35,456	57,061
Real estate – residential mortgage | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,017	8,209
Real estate – residential mortgage | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	17,457	20,215
Real estate – residential mortgage | Current
Financing Receivable, Past Due [Line Items]
Total	5,066,632	4,625,500
Real estate - home equity
Financing Receivable, Past Due [Line Items]
Total	1,061,891	1,102,838
Non- accrual	5,827	6,105
Real estate - home equity | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	5,865	5,666
Real estate - home equity | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,567	2,444
Real estate - home equity | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	3,902	2,704
Real estate - home equity | Current
Financing Receivable, Past Due [Line Items]
Total	1,044,730	1,085,919
Real-estate - construction
Financing Receivable, Past Due [Line Items]
Total	1,308,564	1,269,925
Non- accrual	1,099	1,368
Real-estate - construction | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,719	1,762
Real-estate - construction | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	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	1,305,746	1,265,037
Consumer
Financing Receivable, Past Due [Line Items]
Total	763,530	699,179
Non- accrual	17	92
Consumer | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,482	6,692
Consumer | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,382	1,339
Consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	723	899
Consumer | Current
Financing Receivable, Past Due [Line Items]
Total	754,926	690,157
Leases and other loans
Financing Receivable, Past Due [Line Items]
Total	314,131	298,954
Non- accrual	11,334	13,307
Leases and other loans | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	462	348
Leases and other loans | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	375	122
Leases and other loans | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Leases and other loans | Current
Financing Receivable, Past Due [Line Items]
Total	301,960	285,177
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	0	700
US Government Insured Loan Program | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	$ 1,000	$ 7,700