Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020		Jun. 30, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents
Cash	$ 49,235	[1]	$ 33,131	$ 52,480	[1]	$ 35,685	$ 33,783	$ 38,099
Restricted Cash	1,047		1,043	1,036		1,033	1,031	1,028
Total	$ 50,282		$ 34,174	$ 53,516		$ 36,718	$ 34,814	$ 39,127

[1] Asset and liability amounts in parentheses represent the aggregated balances at September 30, 2020 and December 31, 2019 attributable to Pzena Investment Management Special Situations, LLC, Pzena U.S. Best Ideas (GP), LLC, and Pzena Global Best Ideas (GP), LLC which were variable interest entities as of September 30, 2020 and December 31, 2019, respectively. Asset and liability amounts in parentheses at September 30, 2020 are also attributable to Pzena Global Focus Value Fund. Asset and liability amounts in parentheses at December 31, 2019 are also attributable to Pzena International Value Service (a series of Pzena Investment Management International, LLC).