Revenue from Contracts with Clients (Revenue Disaggregation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 1,168.4	$ 1,063.7
Foreign Exchange Trading Income	80.9	78.7
Treasury Management Fees	11.1	11.2
Security Commissions and Trading Income	36.2	34.8
Other Operating Income	41.1	54.9
Investment Security Gains (Losses), net	0.0	0.0
Total Other Noninterest Income	169.3	179.6
Total Noninterest Income	1,337.7	1,243.3
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Revenue from contract with client	484.0	469.7
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Revenue from contract with client	603.2	516.4
Securities Lending
Disaggregation of Revenue [Line Items]
Revenue from contract with client	18.9	18.3
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 62.3	$ 59.3