Revenue from Contracts with Clients (Contract Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 1,030.7	$ 928.4
Trust Fees Receivable, net
Disaggregation of Revenue [Line Items]
Total Client Receivables	973.6	863.5
Contract with customer, asset, allowance for credit loss	13.5	15.9
Other
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 57.1	$ 64.9