Revenue Recognition - Schedule of Disaggregated Revenue by Source (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net services revenue	$ 379.7	$ 307.2	$ 1,075.7	$ 942.4
Net operating fees
Disaggregation of Revenue [Line Items]
Net services revenue	308.5	253.7	879.8	822.4
Incentive fees
Disaggregation of Revenue [Line Items]
Net services revenue	41.5	25.1	108.0	43.2
Other
Disaggregation of Revenue [Line Items]
Net services revenue	$ 29.7	$ 28.4	$ 87.9	$ 76.8