Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
ENI revenue	$ 95.5	$ 133.3	$ 207.7	$ 243.0
ENI operating expenses	25.6	61.3	64.8	113.2
Earnings before variable compensation	69.9	72.0	142.9	129.8
Variable compensation	22.7	32.7	50.6	56.7
ENI operating earnings (after variable comp)	47.2	39.3	92.3	73.1
Affiliate key employee distributions	0.5	3.2	2.4	4.5
Earnings after Affiliate key employee distributions	46.7	36.1	89.9	68.6
Net interest expense	(4.7)	(6.2)	(11.2)	(12.4)
Net investment income (loss)	(0.7)	4.7	(0.8)	7.3
Gain on sale of Affiliates			0.0	(1.3)
Net income attributable to non-controlling interests in consolidated Funds	0.0	(54.6)	0.0	(68.0)
Income tax expense	(12.7)	(9.9)	(22.3)	(19.0)
Income from discontinued operations, net of tax	0.0	53.4	0.0	75.3
Loss on extinguishment of debt	0.0	0.0	(3.2)	0.0
Gain on disposal of discontinued operations, net of tax	0.0	509.2	0.0	509.2
Net income attributable to controlling interests	28.6	532.7	52.4	559.7
Tax effect	0.0	176.6	0.0	176.6
Operating Segments | Quant & Solutions
Segment Reporting Information [Line Items]
ENI revenue	95.5	111.1	207.7	214.6
ENI operating expenses	39.7	38.3	80.8	77.4
Earnings before variable compensation	55.8	72.8	126.9	137.2
Variable compensation	21.7	22.0	48.0	44.6
ENI operating earnings (after variable comp)	34.1	50.8	78.9	92.6
Affiliate key employee distributions	0.5	3.1	2.4	4.6
Earnings after Affiliate key employee distributions	33.6	47.7	76.5	88.0
Net interest expense	0.0	0.0	0.0	0.0
Net investment income (loss)	0.0	0.0	0.0	0.0
Gain on sale of Affiliates				0.0
Net income attributable to non-controlling interests in consolidated Funds		0.0		0.0
Income tax expense	0.0	0.0	0.0	0.0
Income from discontinued operations, net of tax		0.0		0.0
Loss on extinguishment of debt			0.0
Gain on disposal of discontinued operations, net of tax		0.0		0.0
Net income attributable to controlling interests	33.6	47.7	76.5	88.0
Other
Segment Reporting Information [Line Items]
ENI revenue	0.0	22.3	0.0	28.6
ENI operating expenses	4.4	9.5	8.9	19.2
Earnings before variable compensation	(4.4)	12.8	(8.9)	9.4
Variable compensation	1.0	10.4	2.6	11.3
ENI operating earnings (after variable comp)	(5.4)	2.4	(11.5)	(1.9)
Affiliate key employee distributions	0.0	0.1	0.0	(0.1)
Earnings after Affiliate key employee distributions	(5.4)	2.3	(11.5)	(1.8)
Net interest expense	(4.6)	(5.4)	(9.2)	(10.8)
Net investment income (loss)	0.0	0.0	0.0	0.0
Gain on sale of Affiliates				0.0
Net income attributable to non-controlling interests in consolidated Funds		0.0		0.0
Income tax expense	(6.3)	(11.7)	(15.1)	(20.0)
Income from discontinued operations, net of tax		0.0		0.0
Loss on extinguishment of debt			0.0
Gain on disposal of discontinued operations, net of tax		0.0		0.0
Net income attributable to controlling interests	(16.3)	(14.8)	(35.8)	(32.6)
Reconciling Adjustments
Segment Reporting Information [Line Items]
ENI revenue	0.0	(0.1)	0.0	(0.2)
ENI operating expenses	(18.5)	13.5	(24.9)	16.6
Earnings before variable compensation	18.5	(13.6)	24.9	(16.8)
Variable compensation	0.0	0.3	0.0	0.8
ENI operating earnings (after variable comp)	18.5	(13.9)	24.9	(17.6)
Affiliate key employee distributions	0.0	0.0	0.0	0.0
Earnings after Affiliate key employee distributions	18.5	(13.9)	24.9	(17.6)
Net interest expense	(0.1)	(0.8)	(2.0)	(1.6)
Net investment income (loss)	(0.7)	4.7	(0.8)	7.3
Gain on sale of Affiliates				(1.3)
Net income attributable to non-controlling interests in consolidated Funds		(54.6)		(68.0)
Income tax expense	(6.4)	1.8	(7.2)	1.0
Income from discontinued operations, net of tax		53.4		75.3
Loss on extinguishment of debt			(3.2)
Gain on disposal of discontinued operations, net of tax		509.2		509.2
Net income attributable to controlling interests	$ 11.3	$ 499.8	$ 11.7	$ 504.3