Revenue from Contracts with Clients (Contract Receivables) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 997.1	$ 928.4
Trust Fees Receivable, net
Disaggregation of Revenue [Line Items]
Total Client Receivables	949.4	863.5
Contract with customer, asset, allowance for credit loss	14.8	15.9
Other
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 47.7	$ 64.9