Loans and Leases (Credit Quality Indicator At Amortized Cost By Origination Year) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 5,922.4
2019	4,025.0
2018	1,447.2
2017	1,218.9
2016	1,447.8
PRIOR	3,293.7
REVOLVING LOANS	15,041.0
REVOLVING LOANS CONVERTED TO TERM LOANS	370.3
Total Loans and Leases	32,766.3	$ 31,409.6
Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2020	21.4
2019	44.2
2018	11.9
2017	0.5
2016	0.5
PRIOR	10.2
REVOLVING LOANS	244.9
REVOLVING LOANS CONVERTED TO TERM LOANS	5.1
Total Loans and Leases	338.7
Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8.6
2019	21.5
2018	0.0
2017	0.0
2016	0.0
PRIOR	1.8
REVOLVING LOANS	28.2
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	60.1
Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	12.8
2019	22.7
2018	11.9
2017	0.5
2016	0.5
PRIOR	8.2
REVOLVING LOANS	216.7
REVOLVING LOANS CONVERTED TO TERM LOANS	5.1
Total Loans and Leases	278.4
Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.2
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	0.2
COMMERCIAL
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,980.3
2019	2,344.3
2018	1,037.3
2017	794.0
2016	844.3
PRIOR	1,301.1
REVOLVING LOANS	5,203.9
REVOLVING LOANS CONVERTED TO TERM LOANS	76.5
Total Loans and Leases	14,581.7	14,001.3
COMMERCIAL | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
2020	895.9
2019	1,285.8
2018	626.9
2017	600.2
2016	639.3
PRIOR	666.1
REVOLVING LOANS	4,757.7
REVOLVING LOANS CONVERTED TO TERM LOANS	52.1
Total Loans and Leases	9,524.0	9,091.1
COMMERCIAL | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	245.2
2019	571.6
2018	208.2
2017	142.8
2016	457.8
PRIOR	465.2
REVOLVING LOANS	3,286.6
REVOLVING LOANS CONVERTED TO TERM LOANS	2.0
Total Loans and Leases	5,379.4
COMMERCIAL | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	614.0
2019	579.5
2018	379.7
2017	428.4
2016	143.0
PRIOR	180.4
REVOLVING LOANS	1,346.4
REVOLVING LOANS CONVERTED TO TERM LOANS	50.1
Total Loans and Leases	3,721.5
COMMERCIAL | Commercial and Institutional | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	36.7
2019	134.7
2018	39.0
2017	29.0
2016	38.5
PRIOR	20.5
REVOLVING LOANS	124.7
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	423.1
COMMERCIAL | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	820.4
2019	1,018.9
2018	398.4
2017	183.1
2016	205.0
PRIOR	526.3
REVOLVING LOANS	198.9
REVOLVING LOANS CONVERTED TO TERM LOANS	22.6
Total Loans and Leases	3,373.6	3,104.3
COMMERCIAL | Commercial Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	359.5
2019	205.7
2018	71.8
2017	40.5
2016	24.9
PRIOR	113.4
REVOLVING LOANS	126.5
REVOLVING LOANS CONVERTED TO TERM LOANS	8.9
Total Loans and Leases	951.2
COMMERCIAL | Commercial Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	453.4
2019	758.0
2018	294.1
2017	110.6
2016	178.5
PRIOR	383.9
REVOLVING LOANS	72.4
REVOLVING LOANS CONVERTED TO TERM LOANS	13.7
Total Loans and Leases	2,264.6
COMMERCIAL | Commercial Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7.5
2019	55.2
2018	32.5
2017	32.0
2016	1.6
PRIOR	29.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	157.8
COMMERCIAL | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,051.0
2019	39.6
2018	12.0
2017	10.7
2016	0.0
PRIOR	78.6
REVOLVING LOANS	247.3
REVOLVING LOANS CONVERTED TO TERM LOANS	1.8
Total Loans and Leases	1,441.0	1,576.3
COMMERCIAL | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	790.8
2019	15.9
2018	10.0
2017	10.7
2016	0.0
PRIOR	0.0
REVOLVING LOANS	32.2
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	859.6
COMMERCIAL | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	259.5
2019	0.6
2018	2.0
2017	0.0
2016	0.0
PRIOR	78.6
REVOLVING LOANS	37.2
REVOLVING LOANS CONVERTED TO TERM LOANS	1.8
Total Loans and Leases	379.7
COMMERCIAL | Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.7
2019	23.1
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	177.9
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	201.7
COMMERCIAL | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	30.1
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	30.1	65.6
COMMERCIAL | Lease Financing, net | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	18.5
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	18.5
COMMERCIAL | Lease Financing, net | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	11.6
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	11.6
COMMERCIAL | Lease Financing, net | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	0.0
COMMERCIAL | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	213.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	213.0	164.0
COMMERCIAL | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	97.7
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	97.7
COMMERCIAL | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	115.3
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	115.3
COMMERCIAL | Other | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	0.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,942.1
2019	1,680.7
2018	409.9
2017	424.9
2016	603.5
PRIOR	1,992.6
REVOLVING LOANS	9,837.1
REVOLVING LOANS CONVERTED TO TERM LOANS	293.8
Total Loans and Leases	18,184.6	17,408.3
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
2020	940.3
2019	888.4
2018	208.8
2017	130.8
2016	112.3
PRIOR	231.1
REVOLVING LOANS	9,101.5
REVOLVING LOANS CONVERTED TO TERM LOANS	279.8
Total Loans and Leases	11,893.0	11,071.4
Personal | Private Client | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	466.3
2019	394.3
2018	56.8
2017	67.6
2016	34.2
PRIOR	150.2
REVOLVING LOANS	5,087.1
REVOLVING LOANS CONVERTED TO TERM LOANS	126.1
Total Loans and Leases	6,382.6
Personal | Private Client | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	468.4
2019	493.6
2018	129.6
2017	60.0
2016	78.1
PRIOR	80.9
REVOLVING LOANS	3,952.3
REVOLVING LOANS CONVERTED TO TERM LOANS	145.7
Total Loans and Leases	5,408.6
Personal | Private Client | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5.6
2019	0.5
2018	22.4
2017	3.2
2016	0.0
PRIOR	0.0
REVOLVING LOANS	62.1
REVOLVING LOANS CONVERTED TO TERM LOANS	8.0
Total Loans and Leases	101.8
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,955.8
2019	748.1
2018	189.2
2017	293.6
2016	490.7
PRIOR	1,751.3
REVOLVING LOANS	490.7
REVOLVING LOANS CONVERTED TO TERM LOANS	8.9
Total Loans and Leases	5,928.3	6,095.0
Personal | Residential Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,322.9
2019	396.2
2018	60.9
2017	108.9
2016	254.2
PRIOR	738.0
REVOLVING LOANS	188.2
REVOLVING LOANS CONVERTED TO TERM LOANS	1.5
Total Loans and Leases	3,070.8
Personal | Residential Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	619.8
2019	342.5
2018	126.6
2017	184.2
2016	233.8
PRIOR	904.6
REVOLVING LOANS	270.2
REVOLVING LOANS CONVERTED TO TERM LOANS	7.4
Total Loans and Leases	2,689.1
Personal | Residential Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	13.1
2019	9.4
2018	1.7
2017	0.5
2016	2.7
PRIOR	108.7
REVOLVING LOANS	32.3
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	168.4
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	338.7	174.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	24.6
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	24.6	$ 67.1
Personal | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5.5
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	5.5
Personal | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	19.1
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	19.1
Personal | Other | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0.0
2019	0.0
2018	0.0
2017	0.0
2016	0.0
PRIOR	0.0
REVOLVING LOANS	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0
Total Loans and Leases	$ 0.0