Non-Controlling Interests (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Noncontrolling Interest [Line Items]
Net Income Attributable to Non-Controlling Interests	$ 15,185	$ 14,228	$ 43,213	$ 37,110
Non-Controlling Interests of Pzena Investment Management, LLC
Noncontrolling Interest [Line Items]
Net Income Attributable to Non-Controlling Interests	15,169	14,013	43,200	36,518
Non-Controlling Interests of Consolidated Subsidiaries
Noncontrolling Interest [Line Items]
Net Income Attributable to Non-Controlling Interests	$ 16	$ 215	$ 13	$ 592