Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Non- accrual	$ 134,303	$ 144,443
Total	20,670,188	20,279,547
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	86,389	88,349
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	13,601	20,805
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	30,336	27,463
Current
Financing Receivable, Past Due [Line Items]
Total	20,405,559	19,998,487
Real estate - commercial mortgage
Financing Receivable, Past Due [Line Items]
Non- accrual	58,409	70,161
Total	7,746,920	7,693,835
Real estate - commercial mortgage \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	19,251	10,753
Real estate - commercial mortgage \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,887	4,644
Real estate - commercial mortgage \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,913	2,473
Real estate - commercial mortgage \| Current
Financing Receivable, Past Due [Line Items]
Total	7,664,460	7,605,804
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Non- accrual	31,879	27,116
Total	4,600,696	4,477,537
Commercial and Industrial \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,428	6,067
Commercial and Industrial \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,279	2,289
Commercial and Industrial \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,676	1,172
Commercial and Industrial \| Current
Financing Receivable, Past Due [Line Items]
Total	4,559,434	4,440,893
Real estate – residential mortgage
Financing Receivable, Past Due [Line Items]
Non- accrual	24,427	26,294
Total	4,880,919	4,737,279
Real estate – residential mortgage \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	34,483	57,061
Real estate – residential mortgage \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	5,779	8,209
Real estate – residential mortgage \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	22,149	20,215
Real estate – residential mortgage \| Current
Financing Receivable, Past Due [Line Items]
Total	4,794,081	4,625,500
Real estate - home equity
Financing Receivable, Past Due [Line Items]
Non- accrual	6,034	6,105
Total	1,074,712	1,102,838
Real estate - home equity \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,442	5,666
Real estate - home equity \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,441	2,444
Real estate - home equity \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,316	2,704
Real estate - home equity \| Current
Financing Receivable, Past Due [Line Items]
Total	1,057,479	1,085,919
Real-estate - construction
Financing Receivable, Past Due [Line Items]
Non- accrual	1,278	1,368
Total	1,326,754	1,269,925
Real-estate - construction \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	13,074	1,762
Real-estate - construction \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	751	1,758
Real-estate - construction \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	231	0
Real-estate - construction \| Current
Financing Receivable, Past Due [Line Items]
Total	1,311,420	1,265,037
Consumer
Financing Receivable, Past Due [Line Items]
Non- accrual	25	92
Total	730,775	699,179
Consumer \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	5,840	6,692
Consumer \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,400	1,339
Consumer \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	608	899
Consumer \| Current
Financing Receivable, Past Due [Line Items]
Total	722,902	690,157
Leases and other loans
Financing Receivable, Past Due [Line Items]
Non- accrual	12,251	13,307
Total	309,412	298,954
Leases and other loans \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	871	348
Leases and other loans \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	64	122
Leases and other loans \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	443	0
Leases and other loans \| Current
Financing Receivable, Past Due [Line Items]
Total	295,783	285,177
US Government Insured Loan Program \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,200	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	$ 1,600	$ 7,700