Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
REVENUE	$ 39,252	$ 32,044
Separately Managed Accounts
Disaggregation of Revenue [Line Items]
REVENUE	20,082	17,640
Asset-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	20,082	17,579
Performance-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	0	61
Sub-Advised Accounts
Disaggregation of Revenue [Line Items]
REVENUE	16,451	12,233
Asset-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	15,565	12,081
Decrease in Asset-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	0	(57)
Performance-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	886	209
Pzena Funds
Disaggregation of Revenue [Line Items]
REVENUE	2,719	2,171
Asset-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	2,986	2,171
Expense Cap Reimbursements
Disaggregation of Revenue [Line Items]
REVENUE	(279)	0
Performance-Based Fees
Disaggregation of Revenue [Line Items]
REVENUE	$ 12	$ 0