Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.8.0.1
Summary of Significant Accounting Policies - Additional Information (Detail)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2017
USD ($)
Segment
Unit
Sep. 30, 2016
USD ($)
Dec. 31, 2016
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    
Minimum            
Summary Of Significant Accounting Policies [Line Items]            
Identifiable finite-lived intangible assets, useful life     3 years      
Maximum            
Summary Of Significant Accounting Policies [Line Items]            
Identifiable finite-lived intangible assets, useful life     20 years      
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 62.00%   62.00%     62.00%
Common stock, voting rights     1 vote per share