Loans (Credit Quality Indicator At Amortized Cost By Origination Year) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	$ 8,145.7		$ 8,145.7		$ 7,905.6
2022/2021	4,953.4		4,953.4		5,484.1
2021/2020	4,428.5		4,428.5		2,791.4
2020/2019	1,818.2		1,818.2		2,007.3
2019/2018	1,264.4		1,264.4		746.1
PRIOR	2,829.3		2,829.3		3,012.1
REVOLVING LOANS	19,428.1		19,428.1		20,561.7
REVOLVING LOANS CONVERTED TO TERM LOANS	709.4		709.4		385.0
TOTAL LOANS	43,577.0		43,577.0		42,893.3
2023, Charge-offs			(0.8)
2022, Charge-offs			(4.5)
2021, Charge-offs			0.0
2020, Charge-offs			0.0
2019, Charge-offs			0.0
Prior, Charge-offs			(0.3)
REVOLVING LOANS, Charge-offs			0.0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0.0
Charge-Offs	(0.8)	$ (5.4)	(5.6)	$ (5.5)
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	6,354.0		6,354.0		5,610.6
2022/2021	3,040.2		3,040.2		3,194.9
2021/2020	2,404.0		2,404.0		1,381.6
2020/2019	568.9		568.9		1,021.9
2019/2018	636.2		636.2		390.1
PRIOR	980.3		980.3		1,203.4
REVOLVING LOANS	7,904.1		7,904.1		8,760.2
REVOLVING LOANS CONVERTED TO TERM LOANS	99.6		99.6		72.9
TOTAL LOANS	21,987.3		21,987.3		21,635.6
2023, Charge-offs			0.0
2022, Charge-offs			(4.5)
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	(0.5)	(4.9)	(4.5)	(4.9)
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,058.9		1,058.9		1,548.2
2022/2021	1,429.6		1,429.6		1,858.6
2021/2020	1,613.3		1,613.3		510.6
2020/2019	255.7		255.7		364.1
2019/2018	273.4		273.4		197.3
PRIOR	599.7		599.7		686.0
REVOLVING LOANS	6,739.0		6,739.0		7,199.6
REVOLVING LOANS CONVERTED TO TERM LOANS	91.7		91.7		50.6
TOTAL LOANS	12,061.3		12,061.3		12,415.0
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	355.1		355.1		753.3
2022/2021	539.8		539.8		1,087.5
2021/2020	874.3		874.3		209.8
2020/2019	95.9		95.9		159.3
2019/2018	148.3		148.3		45.9
PRIOR	417.6		417.6		511.3
REVOLVING LOANS	5,148.5		5,148.5		6,032.8
REVOLVING LOANS CONVERTED TO TERM LOANS	16.0		16.0		17.7
TOTAL LOANS	7,595.5		7,595.5		8,817.6
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	689.9		689.9		744.1
2022/2021	818.7		818.7		740.6
2021/2020	669.7		669.7		300.8
2020/2019	147.6		147.6		191.1
2019/2018	125.0		125.0		151.4
PRIOR	180.4		180.4		174.7
REVOLVING LOANS	1,549.0		1,549.0		1,102.3
REVOLVING LOANS CONVERTED TO TERM LOANS	75.3		75.3		32.9
TOTAL LOANS	4,255.6		4,255.6		3,437.9
Commercial | Commercial and Institutional | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	13.9		13.9		50.8
2022/2021	71.1		71.1		30.5
2021/2020	69.3		69.3		0.0
2020/2019	12.2		12.2		13.7
2019/2018	0.1		0.1		0.0
PRIOR	1.7		1.7		0.0
REVOLVING LOANS	41.5		41.5		64.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.4		0.4		0.0
TOTAL LOANS	210.2		210.2		159.5
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,711.3		1,711.3		1,294.9
2022/2021	1,595.3		1,595.3		1,290.1
2021/2020	746.8		746.8		761.4
2020/2019	247.8		247.8		619.9
2019/2018	303.9		303.9		192.8
PRIOR	197.2		197.2		296.0
REVOLVING LOANS	252.9		252.9		297.4
REVOLVING LOANS CONVERTED TO TERM LOANS	7.9		7.9		20.5
TOTAL LOANS	5,063.1		5,063.1		4,773.0
2023, Charge-offs			0.0
2022, Charge-offs			(4.5)
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			(4.5)
Commercial | Commercial Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	334.2		334.2		318.7
2022/2021	331.8		331.8		227.4
2021/2020	183.5		183.5		123.6
2020/2019	19.1		19.1		123.5
2019/2018	40.8		40.8		39.8
PRIOR	45.9		45.9		39.1
REVOLVING LOANS	47.7		47.7		113.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.5		0.5		3.0
TOTAL LOANS	1,003.5		1,003.5		988.5
Commercial | Commercial Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,360.9		1,360.9		968.5
2022/2021	1,260.2		1,260.2		1,040.0
2021/2020	541.7		541.7		637.8
2020/2019	228.7		228.7		447.3
2019/2018	254.9		254.9		153.0
PRIOR	136.7		136.7		256.9
REVOLVING LOANS	202.7		202.7		181.5
REVOLVING LOANS CONVERTED TO TERM LOANS	7.4		7.4		17.5
TOTAL LOANS	3,993.2		3,993.2		3,702.5
Commercial | Commercial Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	16.2		16.2		7.7
2022/2021	3.3		3.3		22.7
2021/2020	21.6		21.6		0.0
2020/2019	0.0		0.0		49.1
2019/2018	8.2		8.2		0.0
PRIOR	14.6		14.6		0.0
REVOLVING LOANS	2.5		2.5		2.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	66.4		66.4		82.0
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,578.7		1,578.7		1,451.0
2022/2021	15.3		15.3		46.2
2021/2020	43.9		43.9		109.6
2020/2019	65.4		65.4		37.9
2019/2018	58.9		58.9		0.0
PRIOR	183.4		183.4		221.4
REVOLVING LOANS	912.2		912.2		1,263.2
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		1.8
TOTAL LOANS	2,857.8		2,857.8		3,131.1
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	842.6		842.6		991.9
2022/2021	0.0		0.0		46.2
2021/2020	43.9		43.9		109.6
2020/2019	65.4		65.4		14.8
2019/2018	35.8		35.8		0.0
PRIOR	3.2		3.2		6.5
REVOLVING LOANS	823.5		823.5		1,158.3
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	1,814.4		1,814.4		2,327.3
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	689.6		689.6		459.0
2022/2021	0.8		0.8		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	23.1		23.1		0.0
PRIOR	180.2		180.2		214.9
REVOLVING LOANS	88.7		88.7		89.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		1.8
TOTAL LOANS	982.4		982.4		765.2
Commercial | Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	46.5		46.5		0.1
2022/2021	14.5		14.5		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		23.1
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		15.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	61.0		61.0		38.6
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	2,005.1		2,005.1		1,316.5
2022/2021	0.0		0.0		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	2,005.1		2,005.1		1,316.5
Commercial | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,190.9		1,190.9		993.9
2022/2021	0.0		0.0		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	1,190.9		1,190.9		993.9
Commercial | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	814.2		814.2		322.6
2022/2021	0.0		0.0		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	814.2		814.2		322.6
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	1,791.7		1,791.7		2,295.0
2022/2021	1,913.2		1,913.2		2,289.2
2021/2020	2,024.5		2,024.5		1,409.8
2020/2019	1,249.3		1,249.3		985.4
2019/2018	628.2		628.2		356.0
PRIOR	1,849.0		1,849.0		1,808.7
REVOLVING LOANS	11,524.0		11,524.0		11,801.5
REVOLVING LOANS CONVERTED TO TERM LOANS	609.8		609.8		312.1
TOTAL LOANS	21,589.7		21,589.7		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			(0.3)
REVOLVING LOANS, Charge-offs			0.0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0.0
Charge-Offs	(0.3)	$ (0.5)	(1.1)	$ (0.6)
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	650.1		650.1		826.7
2022/2021	690.4		690.4		915.0
2021/2020	731.0		731.0		243.0
2020/2019	169.9		169.9		504.9
2019/2018	170.5		170.5		70.7
PRIOR	208.5		208.5		178.5
REVOLVING LOANS	10,845.9		10,845.9		11,084.8
REVOLVING LOANS CONVERTED TO TERM LOANS	602.3		602.3		295.4
TOTAL LOANS	14,068.6		14,068.6		14,119.0
Personal | Private Client | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	326.5		326.5		395.5
2022/2021	218.2		218.2		159.9
2021/2020	44.4		44.4		50.5
2020/2019	70.0		70.0		313.6
2019/2018	15.1		15.1		13.4
PRIOR	25.0		25.0		18.5
REVOLVING LOANS	5,723.2		5,723.2		5,352.5
REVOLVING LOANS CONVERTED TO TERM LOANS	172.8		172.8		28.2
TOTAL LOANS	6,595.2		6,595.2		6,332.1
Personal | Private Client | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	305.3		305.3		430.3
2022/2021	467.8		467.8		755.1
2021/2020	686.6		686.6		192.4
2020/2019	99.9		99.9		191.3
2019/2018	155.4		155.4		38.7
PRIOR	165.7		165.7		160.0
REVOLVING LOANS	5,115.6		5,115.6		5,728.6
REVOLVING LOANS CONVERTED TO TERM LOANS	429.5		429.5		267.2
TOTAL LOANS	7,425.8		7,425.8		7,763.6
Personal | Private Client | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	18.3		18.3		0.9
2022/2021	4.4		4.4		0.0
2021/2020	0.0		0.0		0.1
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		18.6
PRIOR	17.8		17.8		0.0
REVOLVING LOANS	7.1		7.1		3.7
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	47.6		47.6		23.3
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	313.8		313.8		1,225.9
2022/2021	1,198.4		1,198.4		1,330.2
2021/2020	1,253.5		1,253.5		1,166.8
2020/2019	1,079.4		1,079.4		459.2
2019/2018	438.9		438.9		277.5
PRIOR	1,626.7		1,626.7		1,624.9
REVOLVING LOANS	375.1		375.1		320.1
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		8.9
TOTAL LOANS	6,285.8		6,285.8		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			(0.3)
REVOLVING LOANS, Charge-offs			0.0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0.0
Charge-Offs			(1.1)
Personal | Residential Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	198.7		198.7		871.6
2022/2021	536.2		536.2		666.7
2021/2020	565.4		565.4		567.7
2020/2019	405.1		405.1		168.1
2019/2018	154.2		154.2		102.9
PRIOR	729.2		729.2		750.8
REVOLVING LOANS	229.2		229.2		128.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		7.9
TOTAL LOANS	2,818.0		2,818.0		3,264.1
Personal | Residential Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	115.1		115.1		354.3
2022/2021	644.7		644.7		656.7
2021/2020	682.6		682.6		597.6
2020/2019	672.1		672.1		290.0
2019/2018	273.7		273.7		170.9
PRIOR	863.7		863.7		838.2
REVOLVING LOANS	142.9		142.9		180.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		1.0
TOTAL LOANS	3,394.8		3,394.8		3,089.1
Personal | Residential Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	0.0		0.0		0.0
2022/2021	17.5		17.5		6.8
2021/2020	5.5		5.5		1.5
2020/2019	2.2		2.2		1.1
2019/2018	11.0		11.0		3.7
PRIOR	33.8		33.8		35.9
REVOLVING LOANS	3.0		3.0		11.3
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	73.0		73.0		60.3
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	25.1		25.1		27.2
2022/2021	24.4		24.4		44.0
2021/2020	40.0		40.0		0.0
2020/2019	0.0		0.0		21.3
2019/2018	18.8		18.8		7.8
PRIOR	13.8		13.8		5.3
REVOLVING LOANS	303.0		303.0		396.6
REVOLVING LOANS CONVERTED TO TERM LOANS	7.5		7.5		7.8
TOTAL LOANS	432.6		432.6		510.0
Personal | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	16.1		16.1		3.0
2022/2021	3.7		3.7		3.7
2021/2020	0.6		0.6		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		4.6
PRIOR	5.5		5.5		2.3
REVOLVING LOANS	54.0		54.0		124.6
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	79.9		79.9		138.2
Personal | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	9.0		9.0		24.2
2022/2021	20.7		20.7		40.3
2021/2020	39.4		39.4		0.0
2020/2019	0.0		0.0		21.3
2019/2018	18.8		18.8		3.2
PRIOR	8.3		8.3		2.9
REVOLVING LOANS	249.0		249.0		272.0
REVOLVING LOANS CONVERTED TO TERM LOANS	7.5		7.5		7.8
TOTAL LOANS	352.7		352.7		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	802.7		802.7		215.2
2022/2021	0.0		0.0		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	802.7		802.7		215.2
Personal | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	90.5		90.5		190.8
2022/2021	0.0		0.0		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	90.5		90.5		190.8
Personal | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2023/2022	712.2		712.2		24.4
2022/2021	0.0		0.0		0.0
2021/2020	0.0		0.0		0.0
2020/2019	0.0		0.0		0.0
2019/2018	0.0		0.0		0.0
PRIOR	0.0		0.0		0.0
REVOLVING LOANS	0.0		0.0		0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0		0.0		0.0
TOTAL LOANS	$ 712.2		$ 712.2		$ 24.4