Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	$ 33,757.3	$ 31,409.6
Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	369.9
COMMERCIAL
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	15,769.8	14,001.3
COMMERCIAL | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	10,745.8	9,091.1
COMMERCIAL | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	3,262.7	3,104.3
COMMERCIAL | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	1,324.8	1,576.3
COMMERCIAL | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	51.4	65.6
COMMERCIAL | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	385.1	164.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	17,987.5	17,408.3
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	11,621.3	11,071.4
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	5,942.5	6,095.0
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	369.9	174.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	$ 53.8	$ 67.1