Loans (Delinquency Status) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	$ 42,450.5	$ 41,871.6
NONACCRUAL	55.0	76.7
TOTAL LOANS	42,505.5	41,948.3
NONACCRUAL WITH NO ALLOWANCE	22.9	48.2
CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	42,209.6	41,550.2
30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	175.4	258.0
60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	23.8	38.4
90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	41.7	25.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20,649.1	20,390.7
NONACCRUAL	29.7	40.3
TOTAL LOANS	20,678.8	20,431.0
NONACCRUAL WITH NO ALLOWANCE	5.0	21.3
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,542.1	6,555.6
NONACCRUAL	26.9	39.7
TOTAL LOANS	6,569.0	6,595.3
NONACCRUAL WITH NO ALLOWANCE	2.7	21.3
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,155.5	5,272.2
NONACCRUAL	2.3	0.0
TOTAL LOANS	5,157.8	5,272.2
NONACCRUAL WITH NO ALLOWANCE	2.3	0.0
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3,447.6	3,601.8
NONACCRUAL	0.5	0.6
TOTAL LOANS	3,448.1	3,602.4
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	4,020.1	3,603.4
NONACCRUAL	0.0	0.0
TOTAL LOANS	4,020.1	3,603.4
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1,483.8	1,357.7
NONACCRUAL	0.0	0.0
TOTAL LOANS	1,483.8	1,357.7
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20,578.0	20,250.3
Commercial | CURRENT | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,522.4	6,509.6
Commercial | CURRENT | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,106.8	5,222.1
Commercial | CURRENT | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3,447.6	3,601.8
Commercial | CURRENT | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	4,017.7	3,562.4
Commercial | CURRENT | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1,483.5	1,354.4
Commercial | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	33.1	117.5
Commercial | 30 – 59 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	17.2	39.2
Commercial | 30 – 59 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	13.2	37.3
Commercial | 30 – 59 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 30 – 59 DAYS PAST DUE | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	2.4	41.0
Commercial | 30 – 59 DAYS PAST DUE | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.3	0.0
Commercial | 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3.1	4.4
Commercial | 60 – 89 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	2.0	0.8
Commercial | 60 – 89 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1.1	3.6
Commercial | 60 – 89 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	34.9	18.5
Commercial | 90 DAYS OR MORE PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.5	6.0
Commercial | 90 DAYS OR MORE PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	34.4	9.2
Commercial | 90 DAYS OR MORE PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	3.3
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	21,801.4	21,480.9
NONACCRUAL	25.3	36.4
TOTAL LOANS	21,826.7	21,517.3
NONACCRUAL WITH NO ALLOWANCE	17.9	26.9
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	15,653.4	15,162.6
NONACCRUAL	6.3	6.7
TOTAL LOANS	15,659.7	15,169.3
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,985.5	6,091.3
NONACCRUAL	19.0	29.7
TOTAL LOANS	6,004.5	6,121.0
NONACCRUAL WITH NO ALLOWANCE	17.9	26.9
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	162.5	227.0
NONACCRUAL	0.0	0.0
TOTAL LOANS	162.5	227.0
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	21,631.6	21,299.9
Personal | CURRENT | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	15,505.1	15,022.2
Personal | CURRENT | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,964.0	6,050.7
Personal | CURRENT | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	162.5	227.0
Personal | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	142.3	140.5
Personal | 30 – 59 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	121.9	128.8
Personal | 30 – 59 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20.4	11.7
Personal | 30 – 59 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Personal | 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20.7	34.0
Personal | 60 – 89 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20.2	8.5
Personal | 60 – 89 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.5	25.5
Personal | 60 – 89 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Personal | 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6.8	6.5
Personal | 90 DAYS OR MORE PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6.2	3.1
Personal | 90 DAYS OR MORE PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.6	3.4
Personal | 90 DAYS OR MORE PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	$ 0.0	$ 0.0