Investments - Schedule of Consolidated Investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entity
Total Assets	$ 26,375.1	$ 25,868.3
Total Liabilities	12,940.0	12,953.1
RMMC/RMBC
Variable Interest Entity
Total Assets	261.6	228.2
Total Liabilities	24.7	21.2
Other
Variable Interest Entity
Total Assets	2.8	43.3
Total Liabilities	$ 3.3	$ 16.1