Significant Accounting Policies - Basis of Presentation (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Equity method investment, assets	$ 264,300,000	$ 188,687,000
Maximum loss exposure	2,200,000	3,600,000
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Equity method investment, assets	1,800,000	3,200,000
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Pzena International Value Fund
Variable Interest Entity [Line Items]
Equity method investment, assets	20,100,000
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Pzena Global Focused Value Fund
Variable Interest Entity [Line Items]
Equity method investment, assets	26,700,000	3,600,000
Equity Method Investment, Nonconsolidated Investee or Group of Investees | VIEs that are not consolidated
Variable Interest Entity [Line Items]
Equity method investment, assets	234,700,000	$ 265,900,000
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Emerging Markets Select Value Fund
Variable Interest Entity [Line Items]
Equity method investment, assets	$ 10,300,000