Revenue - Schedule of Disaggregation of Revenue (Details) - Management fees - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Management fee revenue	$ 433.3	$ 478.9	$ 582.1
Quant & Solutions | U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	313.1	249.7	261.4
Quant & Solutions | Non-U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	106.3	97.1	109.4
Liquid Alpha | U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	0.0	82.0	145.5
Liquid Alpha | Non-U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	0.0	26.3	42.2
Other Segments | U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	10.2	17.1	18.2
Other Segments | Non-U.S.
Disaggregation of Revenue [Line Items]
Management fee revenue	$ 3.7	$ 6.7	$ 5.4