Loans and Leases (Borrower Ratings) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	$ 30,982.3	$ 32,490.0
1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	16,274.5	17,692.2
4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	14,167.5	14,403.2
6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	540.3	394.6
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	14,136.9	15,175.2
Commercial | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	7,937.4	8,593.9
Commercial | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,918.7	6,462.4
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	280.8	118.9
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	8,834.9	8,728.1
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,782.3	5,477.4
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	2,936.4	3,159.8
Commercial | Commercial and Institutional | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	116.2	90.9
Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	3,248.9	3,228.8
Commercial | Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	1,079.8	1,209.6
Commercial | Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	2,156.5	1,992.2
Commercial | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	12.6	27.0
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	1,492.7	2,701.6
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	776.6	1,625.3
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	564.1	1,075.3
Commercial | Non-U.S. | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	152.0	1.0
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	88.5	90.7
Commercial | Lease Financing, net | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	76.1	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	471.9	426.0
Commercial | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	222.6	203.3
Commercial | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	249.3	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	16,845.4	17,314.8
Personal | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	8,337.1	9,098.3
Personal | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	8,248.8	7,940.8
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	259.5	275.7
Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	6,133.0	6,514.0
Personal | Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	2,568.7	2,745.0
Personal | Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	3,336.3	3,502.3
Personal | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	228.0	266.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	10,637.7	10,733.3
Personal | Private Client | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	5,733.2	6,321.1
Personal | Private Client | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	4,873.0	4,403.2
Personal | Private Client | 6 to 9 Category (Watch List)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	31.5	9.0
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	74.7	67.5
Personal | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	35.2	32.2
Personal | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans and leases	39.5	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