Allowance for Credit Losses (Collateral Dependent Loans and Leases) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 22,143,739	$ 21,779,367
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,584,186	10,210,182
Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,580,386	3,505,802
Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,398,326	2,333,945
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,094,159	6,343,857
Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,748,269	4,024,467
Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	908,518	862,760
Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,437,372	1,456,630
Residential
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,263,710	5,007,970
Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,145,432	3,871,906
Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,118,278	$ 1,136,064
Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	31,641
Residential Real Estate | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Residential Real Estate | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Residential Real Estate | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	424
Residential Real Estate | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Residential Real Estate | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Residential Real Estate | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	28,116
Residential Real Estate | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,101
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,811
Commercial Real Estate | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,259
Commercial Real Estate | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,005
Commercial Real Estate | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	547
Commercial Real Estate | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Commercial Real Estate | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Commercial Real Estate | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Commercial Real Estate | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
General Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,349
General Business Assets | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
General Business Assets | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
General Business Assets | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	669
General Business Assets | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	40
General Business Assets | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,640
General Business Assets | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
General Business Assets | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,949
Other | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,863
Other | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	86
Other | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Total
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	50,750
Total | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,259
Total | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,005
Total | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,503
Total | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	126
Total | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,640
Total | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	28,116
Total | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 3,101