Revenue from Contracts with Clients (Contract Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 1,049.9	$ 996.8
Trust Fees Receivable, net
Disaggregation of Revenue [Line Items]
Total Client Receivables	969.0	932.3
Fee receivable allowance	5.4	12.0
Other
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 80.9	$ 64.5