Revenue from Contracts with Clients (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Trust, investment and other servicing fees	$ 4,432.6	$ 4,361.1	$ 3,995.0
Security commissions and trading income	136.2	140.2	133.2
Other operating income	191.3	243.9	194.0
Securities Commission and Trading
Disaggregation of Revenue [Line Items]
Trust, investment and other servicing fees	116.8	112.1	102.4
Products and Services, Other Operating Income
Disaggregation of Revenue [Line Items]
Trust, investment and other servicing fees	$ 37.2	$ 53.9	$ 42.8