Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.10.0.1
Summary of Significant Accounting Policies - Additional Information (Detail)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
Segment
Unit
Sep. 30, 2017
USD ($)
Dec. 31, 2017
Unit
Jun. 26, 2013
Summary Of Significant Accounting Policies [Line Items]            
Number of operating segment | Segment     1      
Cash equivalents, maximum maturity period     90 days      
Equity method investments, unrealized intercompany profit (loss) not eliminated amount     $ 0      
Number of reporting unit | Unit     1   1  
Impairment charges on goodwill $ 0 $ 0 $ 0 $ 0    
Corporate tax rate     21.00%   35.00%  
Equity or Balanced Portfolios            
Summary Of Significant Accounting Policies [Line Items]            
Percentage of asset management fee on threshold limit     1.00%      
Asset under management, threshold limit 10,000,000   $ 10,000,000      
Percentage of asset management fee on balance     0.60%      
Fixed Income Portfolios            
Summary Of Significant Accounting Policies [Line Items]            
Percentage of asset management fee on threshold limit     0.40%      
Asset under management, threshold limit 10,000,000   $ 10,000,000      
Percentage of asset management fee on balance     0.30%      
Municipal Value Strategy            
Summary Of Significant Accounting Policies [Line Items]            
Percentage of income from asset management fee     0.65%      
Minimum            
Summary Of Significant Accounting Policies [Line Items]            
Identifiable finite-lived intangible assets, useful life     3 years      
Minimum | Private Funds            
Summary Of Significant Accounting Policies [Line Items]            
Prior written notice period to terminate investment management agreements     30 days      
Prior written notice period after receiving the affirmative vote, to terminate investment management agreements     60 days      
Percentage of income from asset management fee     0.25%      
Minimum | Non-discretionary Assets            
Summary Of Significant Accounting Policies [Line Items]            
Percentage of income from asset management fee     0.05%      
Maximum            
Summary Of Significant Accounting Policies [Line Items]            
Identifiable finite-lived intangible assets, useful life     20 years      
Maximum | Private Funds            
Summary Of Significant Accounting Policies [Line Items]            
Prior written notice period to terminate investment management agreements     90 days      
Prior written notice period after receiving the affirmative vote, to terminate investment management agreements     90 days      
Percentage of income from asset management fee     1.50%      
Maximum | Non-discretionary Assets            
Summary Of Significant Accounting Policies [Line Items]            
Percentage of income from asset management fee     0.01%      
Leasehold Improvements            
Summary Of Significant Accounting Policies [Line Items]            
Property, plant and equipment, useful life     10 years      
Other Fixed Assets | Minimum            
Summary Of Significant Accounting Policies [Line Items]            
Property, plant and equipment, useful life     3 years      
Other Fixed Assets | Maximum            
Summary Of Significant Accounting Policies [Line Items]            
Property, plant and equipment, useful life     7 years      
Equity Method Investments            
Summary Of Significant Accounting Policies [Line Items]            
Impairment charges related to equity method investments $ 0 $ 0 $ 0 $ 0    
Class A Common Stock            
Summary Of Significant Accounting Policies [Line Items]            
Common stock, voting rights     1 vote per share      
Class B Common Stock            
Summary Of Significant Accounting Policies [Line Items]            
Common stock, voting rights     1 vote per share      
Class of share exchangeable to another class     One share of Class A common stock      
Silvercrest L.P | Class A Common Stock            
Summary Of Significant Accounting Policies [Line Items]            
Ownership percentage in a subsidiary 62.30%   62.30%     62.30%
Common stock, voting rights     1 vote per share