Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Non- accrual	$ 136,799	$ 143,666
Total	18,476,119	18,325,350
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	46,807	38,977
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	6,767	8,659
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	24,182	8,453
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	18,261,564	18,125,595
Real estate - commercial mortgage
Financing Receivable, Past Due [Line Items]
Non- accrual	50,400	52,815
Total	7,289,376	7,279,080
Real estate - commercial mortgage \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	3,869	1,089
Real estate - commercial mortgage \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	725	1,750
Real estate - commercial mortgage \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	13,790	1,229
Real estate - commercial mortgage \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	7,220,592	7,222,197
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Non- accrual	28,490	30,141
Total	4,156,981	4,208,327
Commercial and Industrial \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	5,107	5,457
Commercial and Industrial \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	606	1,932
Commercial and Industrial \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,702	488
Commercial and Industrial \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	4,121,076	4,170,309
Real estate - residential mortgage
Financing Receivable, Past Due [Line Items]
Non- accrual	33,920	35,269
Total	3,946,741	3,846,750
Real estate - residential mortgage \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	29,343	22,957
Real estate - residential mortgage \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	4,040	2,920
Real estate - residential mortgage \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	5,388	4,130
Real estate - residential mortgage \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	3,874,050	3,781,474
Real-estate - home equity
Financing Receivable, Past Due [Line Items]
Non- accrual	8,145	8,671
Total	1,098,171	1,118,248
Real-estate - home equity \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	4,326	4,369
Real-estate - home equity \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	727	1,154
Real-estate - home equity \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,729	2,253
Real-estate - home equity \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	1,082,244	1,101,801
Real-estate - construction
Financing Receivable, Past Due [Line Items]
Non- accrual	672	901
Total	1,210,340	1,139,779
Real-estate - construction \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,139	1,318
Real-estate - construction \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
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 \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	1,208,529	1,137,560
Consumer
Financing Receivable, Past Due [Line Items]
Non- accrual	175	229
Total	481,551	464,657
Consumer \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,762	3,561
Consumer \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	669	876
Consumer \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	417	353
Consumer \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	477,528	459,638
Equipment lease financing, other and overdrafts
Financing Receivable, Past Due [Line Items]
Non- accrual	14,997	15,640
Total	292,959	268,509
Equipment lease financing, other and overdrafts \| Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	261	226
Equipment lease financing, other and overdrafts \| Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	27
Equipment lease financing, other and overdrafts \| Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	156	0
Equipment lease financing, other and overdrafts \| Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total	$ 277,545	$ 252,616