Loans and Leases (Borrower Ratings) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 33,471.8	$ 33,822.1
1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,820.2	18,079.6
4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,175.0	15,255.1
6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	476.6	487.4
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,527.4	15,902.3
Commercial | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,714.5	9,071.5
Commercial | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,659.3	6,664.3
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	153.6	166.5
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,487.3	9,523.0
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,278.1	6,293.2
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,080.6	3,108.5
Commercial | Commercial and Institutional | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	128.6	121.3
Commercial | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,922.8	4,002.5
Commercial | Real Estate | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,742.3	1,825.7
Commercial | Real Estate | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,157.6	2,134.8
Commercial | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	22.9	42.0
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	253.6	293.9
Commercial | Lease Financing, net | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	200.8	214.3
Commercial | Lease Financing, net | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	52.8	79.6
Commercial | Lease Financing, net | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	0.0	0.0
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,654.0	1,877.8
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	379.9	602.8
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,272.8	1,273.5
Commercial | Non-U.S. | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1.3	1.5
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	209.7	205.1
Commercial | Other | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	113.4	135.5
Commercial | Other | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	95.5	67.9
Commercial | Other | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	0.8	1.7
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,944.4	17,919.8
Personal | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,105.7	9,008.1
Personal | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,515.7	8,590.8
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	323.0	320.9
Personal | Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,542.1	7,841.9
Personal | Real Estate | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,564.4	2,617.8
Personal | Real Estate | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	4,664.3	4,913.9
Personal | Real Estate | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	313.4	310.2
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,375.8	10,052.0
Personal | Private Client | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,526.9	6,373.2
Personal | Private Client | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,839.4	3,668.4
Personal | Private Client | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9.5	10.4
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	26.5	25.9
Personal | Other | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	14.4	17.1
Personal | Other | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	12.0	8.5
Personal | Other | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 0.1	$ 0.3