Loans (Credit Quality Indicator At Amortized Cost By Origination Year) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	$ 13,006.4	$ 7,905.6
2022/2021	4,823.9	5,484.1
2021/2020	4,177.6	2,791.4
2020/2019	1,765.4	2,007.3
2019/2018	1,208.7	746.1
PRIOR	2,681.5	3,012.1
REVOLVING LOANS	19,233.5	20,561.7
REVOLVING LOANS CONVERTED TO TERM LOANS	720.0	385.0
TOTAL LOANS	47,617.0	42,893.3
2023, Charge-offs	(2.1)
2022, Charge-offs	(4.4)
2021, Charge-offs	0.0
2020, Charge-offs	0.0
2019, Charge-offs	0.0
Prior, Charge-offs	(1.0)
Revolving Loans, Charge-offs	0.0
Revolving Loans Converted to Term Loans, Charge-offs	0.0
Charge-offs	(7.5)	(6.0)	$ (0.7)
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS	5,134.2	4,773.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	10,601.2	5,610.6
2022/2021	3,008.8	3,194.9
2021/2020	2,212.4	1,381.6
2020/2019	536.3	1,021.9
2019/2018	590.8	390.1
PRIOR	899.0	1,203.4
REVOLVING LOANS	7,467.6	8,760.2
REVOLVING LOANS CONVERTED TO TERM LOANS	96.7	72.9
TOTAL LOANS	25,412.8	21,635.6
2023, Charge-offs	(1.3)
2022, Charge-offs	(4.4)
2021, Charge-offs	0.0
2020, Charge-offs	0.0
2019, Charge-offs	0.0
Prior, Charge-offs	0.0
Revolving Loans, Charge-offs	0.0
Revolving Loans Converted to Term Loans, Charge-offs	0.0
Charge-offs	(5.7)	(5.3)	(0.3)
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,259.1	1,548.2
2022/2021	1,395.0	1,858.6
2021/2020	1,458.6	510.6
2020/2019	228.8	364.1
2019/2018	257.8	197.3
PRIOR	590.3	686.0
REVOLVING LOANS	6,276.9	7,199.6
REVOLVING LOANS CONVERTED TO TERM LOANS	88.8	50.6
TOTAL LOANS	11,555.3	12,415.0
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	443.9	753.3
2022/2021	534.1	1,087.5
2021/2020	668.3	209.8
2020/2019	78.1	159.3
2019/2018	137.2	45.9
PRIOR	409.9	511.3
REVOLVING LOANS	4,909.8	6,032.8
REVOLVING LOANS CONVERTED TO TERM LOANS	15.0	17.7
TOTAL LOANS	7,196.3	8,817.6
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	801.4	744.1
2022/2021	790.9	740.6
2021/2020	729.5	300.8
2020/2019	138.7	191.1
2019/2018	120.5	151.4
PRIOR	178.7	174.7
REVOLVING LOANS	1,332.4	1,102.3
REVOLVING LOANS CONVERTED TO TERM LOANS	72.0	32.9
TOTAL LOANS	4,164.1	3,437.9
Commercial | Commercial and Institutional | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	13.8	50.8
2022/2021	70.0	30.5
2021/2020	60.8	0.0
2020/2019	12.0	13.7
2019/2018	0.1	0.0
PRIOR	1.7	0.0
REVOLVING LOANS	34.7	64.5
REVOLVING LOANS CONVERTED TO TERM LOANS	1.8	0.0
TOTAL LOANS	194.9	159.5
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,933.2	1,294.9
2022/2021	1,598.7	1,290.1
2021/2020	710.6	761.4
2020/2019	242.3	619.9
2019/2018	298.8	192.8
PRIOR	155.4	296.0
REVOLVING LOANS	187.3	297.4
REVOLVING LOANS CONVERTED TO TERM LOANS	7.9	20.5
TOTAL LOANS	5,134.2	4,773.0
2023, Charge-offs	(0.7)
2022, Charge-offs	(4.4)
2021, Charge-offs	0.0
2020, Charge-offs	0.0
2019, Charge-offs	0.0
Prior, Charge-offs	0.0
Revolving Loans, Charge-offs	0.0
Revolving Loans Converted to Term Loans, Charge-offs	0.0
Charge-offs	(5.1)
Commercial | Commercial Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	403.6	318.7
2022/2021	389.9	227.4
2021/2020	159.1	123.6
2020/2019	23.9	123.5
2019/2018	37.8	39.8
PRIOR	44.8	39.1
REVOLVING LOANS	51.0	113.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	3.0
TOTAL LOANS	1,110.1	988.5
Commercial | Commercial Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,513.5	968.5
2022/2021	1,208.8	1,040.0
2021/2020	521.0	637.8
2020/2019	218.4	447.3
2019/2018	252.8	153.0
PRIOR	96.0	256.9
REVOLVING LOANS	136.3	181.5
REVOLVING LOANS CONVERTED TO TERM LOANS	7.9	17.5
TOTAL LOANS	3,954.7	3,702.5
Commercial | Commercial Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	16.1	7.7
2022/2021	0.0	22.7
2021/2020	30.5	0.0
2020/2019	0.0	49.1
2019/2018	8.2	0.0
PRIOR	14.6	0.0
REVOLVING LOANS	0.0	2.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	69.4	82.0
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,464.1	1,451.0
2022/2021	15.1	46.2
2021/2020	43.2	109.6
2020/2019	65.2	37.9
2019/2018	34.2	0.0
PRIOR	153.3	221.4
REVOLVING LOANS	1,003.4	1,263.2
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	1.8
TOTAL LOANS	2,778.5	3,131.1
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	487.9	991.9
2022/2021	0.0	46.2
2021/2020	43.2	109.6
2020/2019	65.2	14.8
2019/2018	34.2	0.0
PRIOR	3.3	6.5
REVOLVING LOANS	760.0	1,158.3
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	1,393.8	2,327.3
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	974.7	459.0
2022/2021	0.8	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	150.0	214.9
REVOLVING LOANS	243.4	89.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	1.8
TOTAL LOANS	1,368.9	765.2
Commercial | Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1.5	0.1
2022/2021	14.3	0.0
2021/2020	0.0	0.0
2020/2019	0.0	23.1
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	15.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	15.8	38.6
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	5,944.8	1,316.5
2022/2021	0.0	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	5,944.8	1,316.5
2023, Charge-offs	(0.6)
2022, Charge-offs	0.0
2021, Charge-offs	0.0
2020, Charge-offs	0.0
2019, Charge-offs	0.0
Prior, Charge-offs	0.0
Revolving Loans, Charge-offs	0.0
Revolving Loans Converted to Term Loans, Charge-offs	0.0
Charge-offs	(0.6)
Commercial | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	4,313.2	993.9
2022/2021	0.0	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	4,313.2	993.9
Commercial | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,631.6	322.6
2022/2021	0.0	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	1,631.6	322.6
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	2,405.2	2,295.0
2022/2021	1,815.1	2,289.2
2021/2020	1,965.2	1,409.8
2020/2019	1,229.1	985.4
2019/2018	617.9	356.0
PRIOR	1,782.5	1,808.7
REVOLVING LOANS	11,765.9	11,801.5
REVOLVING LOANS CONVERTED TO TERM LOANS	623.3	312.1
TOTAL LOANS	22,204.2	21,257.7
2023, Charge-offs	(0.8)
2022, Charge-offs	0.0
2021, Charge-offs	0.0
2020, Charge-offs	0.0
2019, Charge-offs	0.0
Prior, Charge-offs	(1.0)
Revolving Loans, Charge-offs	0.0
Revolving Loans Converted to Term Loans, Charge-offs	0.0
Charge-offs	(1.8)	(0.7)	$ (0.4)
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	818.4	826.7
2022/2021	629.3	915.0
2021/2020	707.4	243.0
2020/2019	168.4	504.9
2019/2018	167.5	70.7
PRIOR	197.7	178.5
REVOLVING LOANS	11,055.4	11,084.8
REVOLVING LOANS CONVERTED TO TERM LOANS	615.9	295.4
TOTAL LOANS	14,360.0	14,119.0
Personal | Private Client | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	504.7	395.5
2022/2021	140.8	159.9
2021/2020	52.3	50.5
2020/2019	67.5	313.6
2019/2018	8.7	13.4
PRIOR	134.7	18.5
REVOLVING LOANS	5,320.9	5,352.5
REVOLVING LOANS CONVERTED TO TERM LOANS	168.1	28.2
TOTAL LOANS	6,397.7	6,332.1
Personal | Private Client | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	290.1	430.3
2022/2021	488.2	755.1
2021/2020	655.1	192.4
2020/2019	100.9	191.3
2019/2018	158.8	38.7
PRIOR	44.7	160.0
REVOLVING LOANS	5,721.5	5,728.6
REVOLVING LOANS CONVERTED TO TERM LOANS	447.8	267.2
TOTAL LOANS	7,907.1	7,763.6
Personal | Private Client | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	23.6	0.9
2022/2021	0.3	0.0
2021/2020	0.0	0.1
2020/2019	0.0	0.0
2019/2018	0.0	18.6
PRIOR	18.3	0.0
REVOLVING LOANS	13.0	3.7
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	55.2	23.3
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	470.3	1,225.9
2022/2021	1,169.8	1,330.2
2021/2020	1,218.0	1,166.8
2020/2019	1,060.7	459.2
2019/2018	434.0	277.5
PRIOR	1,571.3	1,624.9
REVOLVING LOANS	403.0	320.1
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	8.9
TOTAL LOANS	6,327.1	6,413.5
2023, Charge-offs	(0.8)
2022, Charge-offs	0.0
2021, Charge-offs	0.0
2020, Charge-offs	0.0
2019, Charge-offs	0.0
Prior, Charge-offs	(1.0)
Revolving Loans, Charge-offs	0.0
Revolving Loans Converted to Term Loans, Charge-offs	0.0
Charge-offs	(1.8)
Personal | Residential Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	278.7	871.6
2022/2021	464.0	666.7
2021/2020	500.6	567.7
2020/2019	373.3	168.1
2019/2018	142.4	102.9
PRIOR	722.4	750.8
REVOLVING LOANS	219.8	128.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	7.9
TOTAL LOANS	2,701.2	3,264.1
Personal | Residential Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	191.6	354.3
2022/2021	694.9	656.7
2021/2020	717.4	597.6
2020/2019	686.7	290.0
2019/2018	290.0	170.9
PRIOR	805.3	838.2
REVOLVING LOANS	170.3	180.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	1.0
TOTAL LOANS	3,556.2	3,089.1
Personal | Residential Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	0.0	0.0
2022/2021	10.9	6.8
2021/2020	0.0	1.5
2020/2019	0.7	1.1
2019/2018	1.6	3.7
PRIOR	43.6	35.9
REVOLVING LOANS	12.9	11.3
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	69.7	60.3
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	28.2	27.2
2022/2021	16.0	44.0
2021/2020	39.8	0.0
2020/2019	0.0	21.3
2019/2018	16.4	7.8
PRIOR	13.5	5.3
REVOLVING LOANS	307.5	396.6
REVOLVING LOANS CONVERTED TO TERM LOANS	7.4	7.8
TOTAL LOANS	428.8	510.0
Personal | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	15.5	3.0
2022/2021	0.0	3.7
2021/2020	0.6	0.0
2020/2019	0.0	0.0
2019/2018	0.0	4.6
PRIOR	4.6	2.3
REVOLVING LOANS	71.4	124.6
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	92.1	138.2
Personal | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	12.7	24.2
2022/2021	16.0	40.3
2021/2020	39.2	0.0
2020/2019	0.0	21.3
2019/2018	16.4	3.2
PRIOR	8.9	2.9
REVOLVING LOANS	236.1	272.0
REVOLVING LOANS CONVERTED TO TERM LOANS	7.4	7.8
TOTAL LOANS	336.7	371.7
Personal | Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022		0.0
2022/2021		0.0
2021/2020		0.0
2020/2019		0.0
2019/2018		0.0
PRIOR		0.1
REVOLVING LOANS		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS		0.0
TOTAL LOANS		0.1
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,088.3	215.2
2022/2021	0.0	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	1,088.3	215.2
Personal | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	461.7	190.8
2022/2021	0.0	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	461.7	190.8
Personal | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	626.6	24.4
2022/2021	0.0	0.0
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS	$ 626.6	$ 24.4