Loans and Leases (COVID-19 Loan Modifications Not Considered TDRS) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 contract	Sep. 30, 2019 contract	Sep. 30, 2020 USD ($) contract	Sep. 30, 2019 contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract	11	5	19	34
CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			70,000,000
RECORDED INVESTMENT			$ 105.0
UNPAID PRINCIPAL BALANCE			0.6
DEFERRED INTEREST AMOUNT			$ 0.9
CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			585,000,000
RECORDED INVESTMENT			$ 1,034.3
UNPAID PRINCIPAL BALANCE			10.7
DEFERRED INTEREST AMOUNT			$ 7.9
COMMERCIAL
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract	1	0	3	3
COMMERCIAL | CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			15,000,000
RECORDED INVESTMENT			$ 80.5
UNPAID PRINCIPAL BALANCE			0.3
DEFERRED INTEREST AMOUNT			$ 0.5
COMMERCIAL | CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			205,000,000
RECORDED INVESTMENT			$ 671.9
UNPAID PRINCIPAL BALANCE			7.9
DEFERRED INTEREST AMOUNT			$ 4.8
COMMERCIAL | Commercial and Institutional
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract	1	0	3	1
COMMERCIAL | Commercial and Institutional | CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			13,000,000
RECORDED INVESTMENT			$ 73.2
UNPAID PRINCIPAL BALANCE			0.3
DEFERRED INTEREST AMOUNT			$ 0.5
COMMERCIAL | Commercial and Institutional | CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			101,000,000
RECORDED INVESTMENT			$ 199.7
UNPAID PRINCIPAL BALANCE			5.0
DEFERRED INTEREST AMOUNT			$ 1.5
COMMERCIAL | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract		0		2
COMMERCIAL | Commercial Real Estate | CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			2,000,000
RECORDED INVESTMENT			$ 7.3
UNPAID PRINCIPAL BALANCE			0.0
DEFERRED INTEREST AMOUNT			$ 0.0
COMMERCIAL | Commercial Real Estate | CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			104,000,000
RECORDED INVESTMENT			$ 472.2
UNPAID PRINCIPAL BALANCE			2.9
DEFERRED INTEREST AMOUNT			$ 3.3
Personal
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract	10	5	16	31
Personal | CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			55,000,000
RECORDED INVESTMENT			$ 24.5
UNPAID PRINCIPAL BALANCE			0.3
DEFERRED INTEREST AMOUNT			$ 0.4
Personal | CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			380,000,000
RECORDED INVESTMENT			$ 362.4
UNPAID PRINCIPAL BALANCE			2.8
DEFERRED INTEREST AMOUNT			$ 3.1
Personal | Private Client | CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			2,000,000
RECORDED INVESTMENT			$ 5.2
UNPAID PRINCIPAL BALANCE			0.0
DEFERRED INTEREST AMOUNT			$ 0.1
Personal | Private Client | CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			34,000,000
RECORDED INVESTMENT			$ 177.6
UNPAID PRINCIPAL BALANCE			2.3
DEFERRED INTEREST AMOUNT			$ 1.1
Personal | Residential Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract	10	5	16	31
Personal | Residential Real Estate | CARES Act | Active Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			53,000,000
RECORDED INVESTMENT			$ 19.3
UNPAID PRINCIPAL BALANCE			0.3
DEFERRED INTEREST AMOUNT			$ 0.3
Personal | Residential Real Estate | CARES Act | Completed Deferral
Financing Receivable, Troubled Debt Restructuring [Line Items]
NUMBER OF LOANS AND LEASES | contract			346,000,000
RECORDED INVESTMENT			$ 184.8
UNPAID PRINCIPAL BALANCE			0.5
DEFERRED INTEREST AMOUNT			$ 2.0