Significant Accounting Policies - Additional Information (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2018 USD ($)		Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment		Sep. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)		Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Significant Accounting Policies [Line Items]
Revenue	$ 39,580,000		$ 36,229,000	$ 117,180,000		$ 102,386,000
General and administrative expense	3,322,000		3,062,000	$ 9,856,000		9,585,000
Revenue Recognition
Contract measurement period (in years)				3 years
Cash and Cash Equivalents
Cash and Cash Equivalents	31,913,000	[1]	47,910,000	$ 31,913,000	[1]	47,910,000	$ 52,541,000	$ 63,414,000	[1]	$ 34,749,000	$ 43,522,000
Restricted Cash	1,026,000		4,590,000	1,026,000		4,590,000	1,024,000	1,017,000		4,298,000	3,636,000
Total	32,939,000		52,500,000	32,939,000		52,500,000	$ 53,565,000	64,431,000		$ 39,047,000	$ 47,158,000
Impairment losses recognized	0		0	0		0
Concentration of Credit Risk
Allowance for doubtful accounts receivable	0			$ 0				0
Business Segments
Number of operating segments (in segments) | segment				1
Tax Receivable Agreement:
Valuation allowance on deferred tax assets	$ 0			$ 0				0
Section 754 election tax deduction period				15 years
Cash savings generated by this election will be distributed to selling and converting shareholders upon realization (in hundredth)	85.00%			85.00%
Percentage of cash tax savings in income tax if realizes company expects to benefit	15.00%			15.00%
Cash savings generated by this election will increase additional paid-in capital	15.00%			15.00%
Other comprehensive income (loss) associated with foreign currency translation adjustments (less than $0.1 million)	$ (27,000)		48,000	$ (90,000)		$ 104,000
Maximum
Tax Receivable Agreement:
Other comprehensive income (loss) associated with foreign currency translation adjustments (less than $0.1 million)	$ (100,000)		$ 100,000
Equipment | Minimum
Concentration of Credit Risk
Property and equipment, useful life (years)				3 years
Equipment | Maximum
Concentration of Credit Risk
Property and equipment, useful life (years)				7 years
Largest Customer | Customer Concentration Risk | Advisory fees
Concentration of Credit Risk
Concentration risk (percent)	11.30%		11.20%	11.80%		11.20%
Letter of Credit
Cash and Cash Equivalents
Restricted Cash	$ 1,000,000			$ 1,000,000				$ 1,000,000
Adjustments due to Topic 606 | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue	(200,000)			(600,000)
General and administrative expense	$ (200,000)			$ (600,000)

[1] Asset and liability amounts in parentheses represent the aggregated balances at September 30, 2018 and December 31, 2017 attributable to Pzena International Value Service (a series of Pzena Investment Management, LLC), Pzena Investment Management Special Situations, LLC, and Pzena U.S. Best Ideas (GP), LLC, which were variable interest entities as of September 30, 2018 and December 31, 2017, respectively. Aggregated balances of variable interest entities at September 30, 2018 also reflect Pzena Global Best Ideas (GP), LLC.