Loans (Delinquency Status) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	$ 43,750.7	$ 41,871.6
NONACCRUAL	71.3	76.7
TOTAL LOANS	43,822.0	41,948.3
NONACCRUAL WITH NO ALLOWANCE	22.2	48.2
CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	43,409.0	41,550.2
30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	204.2	258.0
60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	109.5	38.4
90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	28.0	25.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	21,316.1	20,390.7
NONACCRUAL	47.2	40.3
TOTAL LOANS	21,363.3	20,431.0
NONACCRUAL WITH NO ALLOWANCE	4.5	21.3
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,731.4	6,555.6
NONACCRUAL	44.6	39.7
TOTAL LOANS	6,776.0	6,595.3
NONACCRUAL WITH NO ALLOWANCE	2.4	21.3
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,314.1	5,272.2
NONACCRUAL	2.1	0.0
TOTAL LOANS	5,316.2	5,272.2
NONACCRUAL WITH NO ALLOWANCE	2.1	0.0
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3,538.3	3,601.8
NONACCRUAL	0.5	0.6
TOTAL LOANS	3,538.8	3,602.4
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	4,187.8	3,603.4
NONACCRUAL	0.0	0.0
TOTAL LOANS	4,187.8	3,603.4
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1,544.5	1,357.7
NONACCRUAL	0.0	0.0
TOTAL LOANS	1,544.5	1,357.7
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	21,175.2	20,250.3
Commercial | CURRENT | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,721.3	6,509.6
Commercial | CURRENT | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,204.6	5,222.1
Commercial | CURRENT | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3,538.3	3,601.8
Commercial | CURRENT | Subscription Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	4,166.7	3,562.4
Commercial | CURRENT | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1,544.3	1,354.4
Commercial | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	119.1	117.5
Commercial | 30 – 59 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6.8	39.2
Commercial | 30 – 59 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	92.7	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	19.6	41.0
Commercial | 30 – 59 DAYS PAST DUE | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	16.1	4.4
Commercial | 60 – 89 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3.3	0.8
Commercial | 60 – 89 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	11.1	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	1.5	0.0
Commercial | 60 – 89 DAYS PAST DUE | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.2	0.0
Commercial | 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5.7	18.5
Commercial | 90 DAYS OR MORE PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.0	6.0
Commercial | 90 DAYS OR MORE PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5.7	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	22,434.6	21,480.9
NONACCRUAL	24.1	36.4
TOTAL LOANS	22,458.7	21,517.3
NONACCRUAL WITH NO ALLOWANCE	17.7	26.9
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	15,886.5	15,162.6
NONACCRUAL	5.4	6.7
TOTAL LOANS	15,891.9	15,169.3
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,031.8	6,091.3
NONACCRUAL	18.7	29.7
TOTAL LOANS	6,050.5	6,121.0
NONACCRUAL WITH NO ALLOWANCE	17.7	26.9
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	516.3	227.0
NONACCRUAL	0.0	0.0
TOTAL LOANS	516.3	227.0
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	22,233.8	21,299.9
Personal | CURRENT | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	15,693.1	15,022.2
Personal | CURRENT | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,024.4	6,050.7
Personal | CURRENT | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	516.3	227.0
Personal | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	85.1	140.5
Personal | 30 – 59 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	84.0	128.8
Personal | 30 – 59 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1.1	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	93.4	34.0
Personal | 60 – 89 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	91.8	8.5
Personal | 60 – 89 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	1.6	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	22.3	6.5
Personal | 90 DAYS OR MORE PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	17.6	3.1
Personal | 90 DAYS OR MORE PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	4.7	3.4
Personal | 90 DAYS OR MORE PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	$ 0.0	$ 0.0