Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
ENI revenue	$ 86.8	$ 117.9	$ 294.5	$ 360.9
ENI operating expenses	35.8	57.1	100.6	170.3
Earnings before variable compensation	51.0	60.8	193.9	190.6
Variable compensation	19.8	27.1	70.4	83.8
ENI operating earnings (after variable comp)	31.2	33.7	123.5	106.8
Affiliate key employee distributions	1.1	5.0	3.5	9.5
Earnings after Affiliate key employee distributions	30.1	28.7	120.0	97.3
Net interest expense	(4.4)	(6.2)	(15.6)	(18.6)
Net investment loss	(0.4)	0.3	(1.2)	7.6
Gain on sale of subsidiaries		34.6	0.0	33.3
Net loss attributable to non-controlling interests in consolidated Funds	0.0	0.0	0.0	(68.0)
Income tax expense	(7.5)	(14.5)	(29.8)	(33.5)
Income from discontinued operations, net of tax	0.0	1.2	0.0	76.5
Loss on extinguishment of debt	0.0	0.0	(3.2)	0.0
Gain on disposal of discontinued operations, net of tax	0.0	185.4	0.0	694.6
Net income attributable to controlling interests	17.8	229.5	70.2	789.2
Operating Segments | Quant & Solutions
Segment Reporting Information [Line Items]
ENI revenue	86.8	110.6	294.5	325.2
ENI operating expenses	40.4	39.4	121.2	116.8
Earnings before variable compensation	46.4	71.2	173.3	208.4
Variable compensation	18.9	23.5	66.9	68.1
ENI operating earnings (after variable comp)	27.5	47.7	106.4	140.3
Affiliate key employee distributions	1.1	3.8	3.5	8.4
Earnings after Affiliate key employee distributions	26.4	43.9	102.9	131.9
Net interest expense	0.0	0.0	0.0	0.0
Net investment loss	0.0	0.0	0.0	0.0
Gain on sale of subsidiaries		0.0		0.0
Net loss attributable to non-controlling interests in consolidated Funds				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	26.4	43.9	102.9	131.9
Other
Segment Reporting Information [Line Items]
ENI revenue	0.0	6.8	0.0	35.4
ENI operating expenses	4.1	7.6	13.0	26.8
Earnings before variable compensation	(4.1)	(0.8)	(13.0)	8.6
Variable compensation	0.9	3.5	3.5	14.8
ENI operating earnings (after variable comp)	(5.0)	(4.3)	(16.5)	(6.2)
Affiliate key employee distributions	0.0	1.2	0.0	1.1
Earnings after Affiliate key employee distributions	(5.0)	(5.5)	(16.5)	(7.3)
Net interest expense	(4.3)	(5.8)	(13.5)	(16.6)
Net investment loss	0.0	0.0	0.0	0.0
Gain on sale of subsidiaries		0.0		0.0
Net loss attributable to non-controlling interests in consolidated Funds				0.0
Income tax expense	(4.6)	(9.0)	(19.7)	(29.0)
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	(13.9)	(20.3)	(49.7)	(52.9)
Reconciling Adjustments
Segment Reporting Information [Line Items]
ENI revenue	0.0	0.5	0.0	0.3
ENI operating expenses	(8.7)	10.1	(33.6)	26.7
Earnings before variable compensation	8.7	(9.6)	33.6	(26.4)
Variable compensation	0.0	0.1	0.0	0.9
ENI operating earnings (after variable comp)	8.7	(9.7)	33.6	(27.3)
Affiliate key employee distributions	0.0	0.0	0.0	0.0
Earnings after Affiliate key employee distributions	8.7	(9.7)	33.6	(27.3)
Net interest expense	(0.1)	(0.4)	(2.1)	(2.0)
Net investment loss	(0.4)	0.3	(1.2)	7.6
Gain on sale of subsidiaries		34.6		33.3
Net loss attributable to non-controlling interests in consolidated Funds				(68.0)
Income tax expense	(2.9)	(5.5)	(10.1)	(4.5)
Income from discontinued operations, net of tax		1.2		76.5
Loss on extinguishment of debt			(3.2)
Gain on disposal of discontinued operations, net of tax		185.4		694.6
Net income attributable to controlling interests	$ 5.3	$ 205.9	$ 17.0	$ 710.2