Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 37,837.7	$ 31,409.6
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	19,736.8	14,001.3
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	12,327.3	9,091.1
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	3,085.2	3,104.3
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	3,923.0	1,576.3
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	64.8	65.6
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	336.5	164.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	18,100.9	17,408.3
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	11,609.9	11,071.4
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	6,074.3	6,095.0
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	346.9	174.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 69.8	$ 67.1