Allowance for Credit Losses (Collateral Dependent Loans and Leases) (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 21,251,478
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,405,393
Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,613,420
Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,472,187
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,018,386
Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,317,573
Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,208,051
Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,492,762
Residential
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,443,060
Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,193,908
Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,249,152
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	99,095
Residential Real Estate [Member] | 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 [Member] | 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 [Member] | Commercial real estate | Commercial Real Estate, Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Residential Real Estate [Member] | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	763
Residential Real Estate [Member] | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	950
Residential Real Estate [Member] | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Residential Real Estate [Member] | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,648
Residential Real Estate [Member] | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	94,734
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,398
Commercial Real Estate [Member] | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,227
Commercial Real Estate [Member] | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,491
Commercial Real Estate [Member] | Commercial real estate | Commercial Real Estate, Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	598
Commercial Real Estate [Member] | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Commercial Real Estate [Member] | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	82
Commercial Real Estate [Member] | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Commercial Real Estate [Member] | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Commercial Real Estate [Member] | 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 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	24,723
General Business Assets [Member] | 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 [Member] | 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 [Member] | Commercial real estate | Commercial Real Estate, Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
General Business Assets [Member] | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	11,680
General Business Assets [Member] | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	8
General Business Assets [Member] | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	13,035
General Business Assets [Member] | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
General Business Assets [Member] | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other Collateral [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,426
Other Collateral [Member] | 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 Collateral [Member] | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other Collateral [Member] | Commercial real estate | Commercial Real Estate, Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other Collateral [Member] | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other Collateral [Member] | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,426
Other Collateral [Member] | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other Collateral [Member] | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Other Collateral [Member] | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	0
Collateral Pledged [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	135,642
Collateral Pledged [Member] | Commercial real estate | Non-owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,227
Collateral Pledged [Member] | Commercial real estate | Owner occupied term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,491
Collateral Pledged [Member] | Commercial real estate | Commercial Real Estate, Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	598
Collateral Pledged [Member] | Commercial | Term, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	12,443
Collateral Pledged [Member] | Commercial | Lines of credit & other, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,466
Collateral Pledged [Member] | Commercial | Leases & equipment finance, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	13,035
Collateral Pledged [Member] | Residential | Mortgage, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,648
Collateral Pledged [Member] | Residential | Home equity loans & lines, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 94,734