Goodwill and Intangible Assets - Changes in Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Nov. 30, 2020
Goodwill [Roll Forward]
Goodwill gross, beginning balance	$ 27,100,000	$ 145,500,000
Accumulated impairment, beginning balance	(6,800,000)	(32,700,000)
Goodwill, beginning balance	20,300,000	112,800,000
Additions	0	0
Impairments	0	(16,400,000)
Disposals (1)	0	(76,100,000)
Goodwill gross, ending balance	22,100,000	27,100,000	$ 145,500,000
Accumulated impairment, ending balance	(1,800,000)	(6,800,000)	(32,700,000)
Goodwill, ending balance	20,300,000	20,300,000	112,800,000
Goodwill	0	161,800,000
Copper Rock
Goodwill [Roll Forward]
Impairments	0	(16,400,000)
Consolidated Entity Excluding Consolidated Funds
Goodwill [Roll Forward]
Goodwill, beginning balance	20,300,000
Impairments	0	(16,400,000)	0
Goodwill, ending balance	20,300,000	20,300,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Barrow, Hanley, Mewhinney & Strauss LLC | Consolidated Entity Excluding Consolidated Funds
Goodwill [Roll Forward]
Goodwill				$ 76,100,000
Quant & Solutions
Goodwill [Roll Forward]
Goodwill gross, beginning balance	22,100,000	22,100,000
Accumulated impairment, beginning balance	(1,800,000)	(1,800,000)
Goodwill, beginning balance	20,300,000	20,300,000
Additions	0	0
Impairments	0	0
Disposals (1)	0	0
Goodwill gross, ending balance	22,100,000	22,100,000	22,100,000
Accumulated impairment, ending balance	(1,800,000)	(1,800,000)	(1,800,000)
Goodwill, ending balance	20,300,000	20,300,000	20,300,000
Alternatives
Goodwill [Roll Forward]
Goodwill gross, beginning balance	5,000,000.0	5,000,000.0
Accumulated impairment, beginning balance	(5,000,000.0)	(5,000,000.0)
Goodwill, beginning balance	0	0
Additions	0	0
Impairments	0	0
Disposals (1)	0	0
Goodwill gross, ending balance	0	5,000,000.0	5,000,000.0
Accumulated impairment, ending balance	0	(5,000,000.0)	(5,000,000.0)
Goodwill, ending balance	0	0	0
Liquid Alpha
Goodwill [Roll Forward]
Goodwill gross, beginning balance	0	118,400,000
Accumulated impairment, beginning balance	0	(25,900,000)
Goodwill, beginning balance	0	92,500,000
Additions	0	0
Impairments	0	(16,400,000)
Disposals (1)	0	(76,100,000)
Goodwill gross, ending balance	0	0	118,400,000
Accumulated impairment, ending balance	0	0	(25,900,000)
Goodwill, ending balance	$ 0	$ 0	$ 92,500,000