Loans and Leases (Credit Quality Indicator At Amortized Cost By Origination Year) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	$ 2,955.4	$ 7,448.6
2020/2019	6,098.2	3,667.9
2019/2018	3,311.5	1,352.6
2018/2017	1,243.5	1,123.1
2017/2016	1,007.9	1,254.8
PRIOR	3,926.4	3,128.5
REVOLVING LOANS	15,462.4	15,453.6
REVOLVING LOANS CONVERTED TO TERM LOANS	339.0	330.6
TOTAL LOANS AND LEASES	34,344.3	33,759.7
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	2,103.8	3,772.7
2020/2019	2,637.9	2,187.7
2019/2018	1,936.7	990.3
2018/2017	915.4	725.0
2017/2016	661.7	749.9
PRIOR	1,863.1	1,285.8
REVOLVING LOANS	5,680.5	5,490.9
REVOLVING LOANS CONVERTED TO TERM LOANS	48.8	59.7
TOTAL LOANS AND LEASES	15,847.9	15,262.0
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	560.2	1,491.5
2020/2019	1,384.6	1,170.9
2019/2018	935.3	596.0
2018/2017	555.8	544.2
2017/2016	486.6	553.6
PRIOR	1,099.0	622.1
REVOLVING LOANS	5,016.8	5,042.2
REVOLVING LOANS CONVERTED TO TERM LOANS	34.8	37.8
TOTAL LOANS AND LEASES	10,073.1	10,058.3
Commercial | Commercial and Institutional | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	334.2	663.8
2020/2019	653.5	546.0
2019/2018	332.8	204.6
2018/2017	179.2	96.0
2017/2016	103.4	396.0
PRIOR	786.0	448.8
REVOLVING LOANS	3,597.0	3,742.4
REVOLVING LOANS CONVERTED TO TERM LOANS	1.2	5.5
TOTAL LOANS AND LEASES	5,987.3	6,103.1
Commercial | Commercial and Institutional | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	196.1	793.4
2020/2019	697.7	505.1
2019/2018	524.6	354.1
2018/2017	339.9	405.4
2017/2016	343.7	134.6
PRIOR	288.1	167.3
REVOLVING LOANS	1,351.5	1,238.7
REVOLVING LOANS CONVERTED TO TERM LOANS	33.6	32.3
TOTAL LOANS AND LEASES	3,775.2	3,630.9
Commercial | Commercial and Institutional | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	29.9	34.3
2020/2019	33.4	119.8
2019/2018	77.9	37.3
2018/2017	36.7	42.8
2017/2016	39.5	23.0
PRIOR	24.9	6.0
REVOLVING LOANS	68.3	61.1
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	310.6	324.3
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	258.2	1,124.7
2020/2019	1,112.4	976.2
2019/2018	960.6	392.3
2018/2017	357.5	169.7
2017/2016	164.0	196.3
PRIOR	667.6	494.4
REVOLVING LOANS	181.4	184.7
REVOLVING LOANS CONVERTED TO TERM LOANS	12.2	20.1
TOTAL LOANS AND LEASES	3,713.9	3,558.4
Commercial | Commercial Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	124.7	406.3
2020/2019	341.5	109.2
2019/2018	153.4	27.6
2018/2017	59.8	36.5
2017/2016	24.3	11.8
PRIOR	113.5	99.4
REVOLVING LOANS	82.6	124.3
REVOLVING LOANS CONVERTED TO TERM LOANS	2.8	8.7
TOTAL LOANS AND LEASES	902.6	823.8
Commercial | Commercial Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	121.4	703.1
2020/2019	752.7	811.8
2019/2018	752.0	332.7
2018/2017	282.2	107.4
2017/2016	115.8	184.5
PRIOR	542.7	382.8
REVOLVING LOANS	98.8	60.4
REVOLVING LOANS CONVERTED TO TERM LOANS	9.4	11.4
TOTAL LOANS AND LEASES	2,675.0	2,594.1
Commercial | Commercial Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	12.1	15.3
2020/2019	18.2	55.2
2019/2018	55.2	32.0
2018/2017	15.5	25.8
2017/2016	23.9	0.0
PRIOR	11.4	12.2
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	136.3	140.5
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	1,007.0	868.3
2020/2019	140.9	40.6
2019/2018	40.8	2.0
2018/2017	2.1	11.1
2017/2016	11.1	0.0
PRIOR	85.2	157.9
REVOLVING LOANS	482.3	264.0
REVOLVING LOANS CONVERTED TO TERM LOANS	1.8	1.8
TOTAL LOANS AND LEASES	1,771.2	1,345.7
Commercial | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	724.7	555.2
2020/2019	112.9	16.8
2019/2018	17.0	0.0
2018/2017	0.0	11.1
2017/2016	11.1	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	270.0	78.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	1,135.7	661.6
Commercial | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	282.1	313.1
2020/2019	28.0	0.7
2019/2018	0.7	2.0
2018/2017	2.1	0.0
2017/2016	0.0	0.0
PRIOR	85.2	157.9
REVOLVING LOANS	129.5	39.2
REVOLVING LOANS CONVERTED TO TERM LOANS	1.8	1.8
TOTAL LOANS AND LEASES	529.4	514.7
Commercial | Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.2	0.0
2020/2019	0.0	23.1
2019/2018	23.1	0.0
2018/2017	0.0	0.0
2017/2016	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	82.8	146.3
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	106.1	169.4
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	0.0	0.0
PRIOR	11.3	11.4
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	11.3	11.4
Commercial | Lease Financing, net | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	0.0	0.0
PRIOR	11.3	11.4
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	11.3	11.4
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	278.4	288.2
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	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 AND LEASES	278.4	288.2
Commercial | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	135.8	81.7
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	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 AND LEASES	135.8	81.7
Commercial | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	142.6	206.5
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	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 AND LEASES	142.6	206.5
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	851.6	3,675.9
2020/2019	3,460.3	1,480.2
2019/2018	1,374.8	362.3
2018/2017	328.1	398.1
2017/2016	346.2	504.9
PRIOR	2,063.3	1,842.7
REVOLVING LOANS	9,781.9	9,962.7
REVOLVING LOANS CONVERTED TO TERM LOANS	290.2	270.9
TOTAL LOANS AND LEASES	18,496.4	18,497.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	280.2	1,166.7
2020/2019	1,108.6	754.1
2019/2018	718.7	191.1
2018/2017	180.5	124.0
2017/2016	118.7	87.7
PRIOR	241.5	213.6
REVOLVING LOANS	9,128.3	9,021.2
REVOLVING LOANS CONVERTED TO TERM LOANS	271.0	256.7
TOTAL LOANS AND LEASES	12,047.5	11,815.1
Personal | Private Client | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	50.9	668.6
2020/2019	567.3	273.7
2019/2018	122.5	51.7
2018/2017	43.7	60.4
2017/2016	54.5	10.2
PRIOR	141.5	136.1
REVOLVING LOANS	5,283.6	5,392.8
REVOLVING LOANS CONVERTED TO TERM LOANS	59.1	47.9
TOTAL LOANS AND LEASES	6,323.1	6,641.4
Personal | Private Client | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	229.2	492.1
2020/2019	535.5	479.9
2019/2018	595.7	117.3
2018/2017	115.1	60.4
2017/2016	64.2	77.5
PRIOR	100.0	77.5
REVOLVING LOANS	3,805.1	3,564.7
REVOLVING LOANS CONVERTED TO TERM LOANS	210.6	207.3
TOTAL LOANS AND LEASES	5,655.4	5,076.7
Personal | Private Client | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.1	6.0
2020/2019	5.8	0.5
2019/2018	0.5	22.1
2018/2017	21.7	3.2
2017/2016	0.0	0.0
PRIOR	0.0	0.0
REVOLVING LOANS	39.6	63.7
REVOLVING LOANS CONVERTED TO TERM LOANS	1.3	1.5
TOTAL LOANS AND LEASES	69.0	97.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	526.1	2,424.2
2020/2019	2,332.3	685.2
2019/2018	615.6	159.4
2018/2017	136.9	273.6
2017/2016	227.1	416.7
PRIOR	1,811.6	1,619.1
REVOLVING LOANS	411.7	448.4
REVOLVING LOANS CONVERTED TO TERM LOANS	5.6	9.1
TOTAL LOANS AND LEASES	6,066.9	6,035.7
Personal | Residential Real Estate | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	375.1	1,554.3
2020/2019	1,440.3	317.4
2019/2018	247.7	42.9
2018/2017	25.3	109.9
2017/2016	99.1	205.1
PRIOR	771.4	627.8
REVOLVING LOANS	143.7	152.8
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	1.7
TOTAL LOANS AND LEASES	3,102.6	3,011.9
Personal | Residential Real Estate | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	150.7	854.6
2020/2019	877.9	359.5
2019/2018	359.8	115.8
2018/2017	111.0	163.2
2017/2016	127.5	209.7
PRIOR	957.6	896.5
REVOLVING LOANS	245.4	273.1
REVOLVING LOANS CONVERTED TO TERM LOANS	5.6	7.4
TOTAL LOANS AND LEASES	2,835.5	2,879.8
Personal | Residential Real Estate | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.3	15.3
2020/2019	14.1	8.3
2019/2018	8.1	0.7
2018/2017	0.6	0.5
2017/2016	0.5	1.9
PRIOR	82.6	94.8
REVOLVING LOANS	22.6	22.5
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	128.8	144.0
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.0	36.0
2020/2019	19.4	40.9
2019/2018	40.5	11.8
2018/2017	10.7	0.5
2017/2016	0.4	0.5
PRIOR	10.2	10.0
REVOLVING LOANS	241.9	493.1
REVOLVING LOANS CONVERTED TO TERM LOANS	13.6	5.1
TOTAL LOANS AND LEASES	336.7	597.9
Personal | Non-U.S. | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.0	23.3
2020/2019	9.2	14.9
2019/2018	32.3	0.0
2018/2017	0.0	0.0
2017/2016	0.0	0.0
PRIOR	1.1	1.8
REVOLVING LOANS	65.9	275.6
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	108.5	315.6
Personal | Non-U.S. | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.0	12.7
2020/2019	10.2	26.0
2019/2018	8.2	11.8
2018/2017	10.7	0.5
2017/2016	0.4	0.5
PRIOR	8.8	7.9
REVOLVING LOANS	176.0	217.5
REVOLVING LOANS CONVERTED TO TERM LOANS	13.6	5.1
TOTAL LOANS AND LEASES	227.9	282.0
Personal | Non-U.S. | 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	0.0	0.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	0.0	0.0
PRIOR	0.3	0.3
REVOLVING LOANS	0.0	0.0
REVOLVING LOANS CONVERTED TO TERM LOANS	0.0	0.0
TOTAL LOANS AND LEASES	0.3	0.3
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	45.3	49.0
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	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 AND LEASES	45.3	49.0
Personal | Other | 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	26.8	34.6
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	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 AND LEASES	26.8	34.6
Personal | Other | 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2021/2020	18.5	14.4
2020/2019	0.0	0.0
2019/2018	0.0	0.0
2018/2017	0.0	0.0
2017/2016	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 AND LEASES	$ 18.5	$ 14.4