Revenue from Contracts with Clients (Contract Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 960.4	$ 937.9
Trust Fees Receivable, net
Disaggregation of Revenue [Line Items]
Total Client Receivables	903.0	882.5
Contract with customer, asset, allowance for credit loss	14.6	13.5
Other
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 57.4	$ 55.4