Revenue from Contracts with Clients (Revenue Disaggregation) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 1,078.7	$ 1,111.0	$ 3,390.5	$ 3,250.1
Foreign Exchange Trading Income	64.7	66.4	223.2	215.7
Treasury Management Fees	9.3	11.2	31.0	33.7
Security Commissions and Trading Income	32.1	36.5	101.1	104.3
Other Operating Income	57.3	62.3	144.0	171.6
Investment Security Gains (Losses), net	(0.3)	0.0	(0.3)	0.0
Total Other Noninterest Income	163.1	176.4	499.0	525.3
Total Noninterest Income	1,241.8	1,287.4	3,889.5	3,775.4
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Revenue from contract with client	435.0	485.9	1,383.4	1,434.8
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Revenue from contract with client	565.3	549.2	1,765.8	1,586.8
Securities Lending
Disaggregation of Revenue [Line Items]
Revenue from contract with client	21.7	20.2	62.2	58.0
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 56.7	$ 55.7	$ 179.1	$ 170.5