Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) segment		Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)
Significant Accounting Policies [Line Items]
Revenue	$ 39,252,000		$ 32,044,000
General and administrative expense	$ 3,155,000		3,325,000
Revenue Recognition
Contract measurement period (in years)	3 years
Cash and Cash Equivalents
Cash	$ 27,347,000	[1]	20,047,000	$ 63,414,000	[1]	$ 43,522,000
Restricted Cash	1,021,000		3,831,000	1,017,000		3,636,000
Total Cash and Restricted Cash at end of period	28,368,000		23,878,000	64,431,000		$ 47,158,000
Impairment losses recognized	0		0
Concentration of Credit Risk
Allowance for doubtful accounts receivable	$ 0			0
Business Segments
Number of operating segments (in segments) | segment	1
Tax Receivable Agreement:
Valuation allowance on deferred tax assets	$ 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%
Percentage of cash tax savings in income tax if realizes company expects to benefit	15.00%
Cash savings generated by this election will increase additional paid-in capital	15.00%
Other comprehensive income associated with foreign currency translation adjustments (less than $0.1 million)	$ 68,000		$ 12,000
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
Letter of Credit
Cash and Cash Equivalents
Restricted Cash				$ 1,000,000
Largest Customer | Customer Concentration Risk | Advisory fees
Concentration of Credit Risk
Concentration risk (percent)	12.20%		11.20%
Adjustments due to Topic 606 | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Revenue	$ (300,000)
General and administrative expense	$ (300,000)

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