Revenue from Contracts with Clients (Revenue Disaggregated by Major Source) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 4,727.8	$ 4,361.8	$ 4,432.6
Foreign Exchange Trading Income	231.2	203.9	288.6
Treasury Management Fees	35.7	31.6	39.3
Security Commissions and Trading Income	150.5	135.0	136.2
Other Operating Income	1,157.4	228.7	191.3
Investment Security Gains (Losses), net	(189.3)	(169.5)	(214.0)
Total Other Noninterest Income	1,385.5	429.7	441.4
Total Noninterest Income	6,113.3	4,791.5	4,874.0
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	1,915.2	1,805.3	1,816.0
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	2,491.5	2,232.3	2,299.1
Securities Lending
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	74.3	83.9	81.6
Other
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 246.8	$ 240.3	$ 235.9