Earnings per Share - Diluted Net Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Diluted Net Income [Abstract]
Net Income Attributable to Non-Controlling Interests	$ 14,143	$ 10,390
Net Income of Pzena Investment Management, Inc.	3,523	2,336
Diluted Net Income	14,226	8,704
Pzena Investment Management, LLC
Diluted Net Income [Abstract]
Net Income Attributable to Non-Controlling Interests	14,113	10,120
Less: Assumed Corporate Income Taxes	3,410	3,752
Assumed After-Tax Income of Pzena Investment Management, LLC	10,703	6,368
Net Income of Pzena Investment Management, Inc.	3,523	2,336
Diluted Net Income	$ 14,226	$ 8,704