Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Schedule of Reconciliation of Cash and Cash Equivalents Inclusive of Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Supplemental Cash Flow Elements [Abstract]
Restricted fiduciary cash	$ 1,210.8	$ 1,231.9
Non-restricted fiduciary cash	169.2	151.3
Total restricted and non-restricted fiduciary cash at the end of the period	1,380.0	1,383.2
Cash and cash equivalents	563.5	650.0
Total cash, cash equivalents and fiduciary cash at the end of the period	$ 1,943.5	$ 2,033.2	$ 2,426.1	$ 1,470.2