Revenue from Contracts with Clients (Revenue Disaggregation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 1,063.6	$ 1,168.4
Foreign Exchange Trading Income	53.0	80.9
Treasury Management Fees	8.4	11.1
Security Commissions and Trading Income	34.7	36.2
Other Operating Income	46.8	41.1
Investment Security Gains (Losses), net	6.9	0.0
Total Other Noninterest Income	149.8	169.3
Total Noninterest Income	1,213.4	1,337.7
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Revenue from contract with client	441.6	484.0
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Revenue from contract with client	540.5	603.2
Securities Lending
Disaggregation of Revenue [Line Items]
Revenue from contract with client	19.1	18.9
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 62.4	$ 62.3