Revenue from Contracts with Clients (Revenue Disaggregation) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 1,143.4	$ 1,075.4	$ 2,311.8	$ 2,139.1
Foreign Exchange Trading Income	77.6	70.6	158.5	149.3
Treasury Management Fees	10.6	11.3	21.7	22.5
Security Commissions and Trading Income	32.8	33.0	69.0	67.8
Other Operating Income	45.6	54.4	86.7	109.3
Investment Security Gains (Losses), net	0.0	0.0	0.0	0.0
Total Other Noninterest Income	166.6	169.3	335.9	348.9
Total Noninterest Income	1,310.0	1,244.7	2,647.7	2,488.0
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Revenue from contract with client	464.4	479.2	948.4	948.9
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Revenue from contract with client	597.3	521.2	1,200.5	1,037.6
Securities Lending
Disaggregation of Revenue [Line Items]
Revenue from contract with client	21.6	19.5	40.5	37.8
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with client	$ 60.1	$ 55.5	$ 122.4	$ 114.8