Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	$ 32,766.3	$ 31,409.6
Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	338.7
COMMERCIAL
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	14,581.7	14,001.3
COMMERCIAL | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	9,524.0	9,091.1
COMMERCIAL | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	3,373.6	3,104.3
COMMERCIAL | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	1,441.0	1,576.3
COMMERCIAL | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	30.1	65.6
COMMERCIAL | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	213.0	164.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	18,184.6	17,408.3
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	11,893.0	11,071.4
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	5,928.3	6,095.0
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	338.7	174.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	$ 24.6	$ 67.1