Revenue - Schedule of Disaggregation of Revenue (Details) - Management fees - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Management fee revenue	$ 85.7	$ 111.4	$ 281.4	$ 326.8
Quant & Solutions | U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	64.9	80.3	213.1	234.7
Quant & Solutions | Non-U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	20.8	27.7	68.3	78.2
Other | U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	0.0	2.4	0.0	10.2
Other | Non-U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	$ 0.0	$ 1.0	$ 0.0	$ 3.7