Loans and Leases (Borrower Ratings) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	$ 30,844.2	$ 32,490.0
1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	16,040.6	17,692.2
4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	14,269.7	14,403.2
6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	533.9	394.6
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	13,981.9	15,175.2
Commercial | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	7,795.8	8,593.9
Commercial | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,913.2	6,462.4
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	272.9	118.9
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	8,623.8	8,728.1
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,586.7	5,477.4
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	2,917.0	3,159.8
Commercial | Commercial and Institutional | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	120.1	90.9
Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	3,227.6	3,228.8
Commercial | Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	967.9	1,209.6
Commercial | Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	2,247.2	1,992.2
Commercial | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	12.5	27.0
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	1,478.3	2,701.6
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	755.1	1,625.3
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	582.9	1,075.3
Commercial | Non-U.S. | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	140.3	1.0
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	87.6	90.7
Commercial | Lease Financing, net | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	75.2	78.3
Commercial | Lease Financing, net | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	12.4	12.4
Commercial | Lease Financing, net | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	0.0	0.0
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	564.6	426.0
Commercial | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	410.9	203.3
Commercial | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	153.7	222.7
Commercial | Other | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	0.0	0.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	16,862.3	17,314.8
Personal | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	8,244.8	9,098.3
Personal | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	8,356.5	7,940.8
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	261.0	275.7
Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	6,066.3	6,514.0
Personal | Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	2,578.3	2,745.0
Personal | Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	3,272.0	3,502.3
Personal | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	216.0	266.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	10,706.6	10,733.3
Personal | Private Client | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,601.4	6,321.1
Personal | Private Client | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,060.2	4,403.2
Personal | Private Client | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	45.0	9.0
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	89.4	67.5
Personal | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	65.1	32.2
Personal | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	24.3	35.3
Personal | Other | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	$ 0.0	$ 0.0