Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2021		Mar. 31, 2021	Dec. 31, 2020		Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents
Cash	$ 53,463	[1]	$ 29,650	$ 65,534	[1]	$ 33,131	$ 20,527	$ 52,480
Restricted Cash	1,054		1,054	1,050		1,043	1,040	1,036
Total	$ 54,517		$ 30,704	$ 66,584		$ 34,174	$ 21,567	$ 53,516

[1] Asset and liability amounts in parentheses represent the aggregated balances at June 30, 2021 and December 31, 2020 attributable to Pzena Investment Management Special Situations, LLC, Pzena U.S. Best Ideas (GP), LLC, Pzena Global Best Ideas (GP), LLC, and Pzena Global Focus Value Fund which were variable interest entities as of June 30, 2021 and December 31, 2020, respectively.