Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

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Stockholders' Equity - Additional Information (Detail) - USD ($)
$ in Thousands
 1 Months Ended 3 Months Ended 9 Months Ended
Aug. 31, 2015
Jun. 30, 2015
May. 31, 2015
Mar. 31, 2015
Feb. 28, 2015
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Class Of Stock [Line Items]                  
Partnership distributions, amount           $ 1,446 $ 1,248 $ 5,571 $ 5,244
Distributions of partner incentive allocations of net income               $ 18,568 $ 14,206
2012 Equity Incentive Plan                  
Class Of Stock [Line Items]                  
Restricted stock units granted 966,510                
Restricted stock units granted description               Twenty-five percent of the restricted stock units granted vest and settle on each of the first, second, third and fourth anniversaries of the grant date.  
2012 Equity Incentive Plan | First Anniversary                  
Class Of Stock [Line Items]                  
Restricted stock, vesting percentage 25.00%                
2012 Equity Incentive Plan | Second Anniversary                  
Class Of Stock [Line Items]                  
Restricted stock, vesting percentage 25.00%                
2012 Equity Incentive Plan | Third Anniversary                  
Class Of Stock [Line Items]                  
Restricted stock, vesting percentage 25.00%                
2012 Equity Incentive Plan | Fourth Anniversary                  
Class Of Stock [Line Items]                  
Restricted stock, vesting percentage 25.00%                
Class B Common Stock                  
Class Of Stock [Line Items]                  
Common stock issued         126,616        
Exchange of Class B common stock for Class A common stock               (134,000) (136,000)
Restricted stock units granted               966,510  
Class B Common Stock | Jamison                  
Class Of Stock [Line Items]                  
Common stock issued   258,578              
Class B Common Stock | Resale And Registration Rights Agreement                  
Class Of Stock [Line Items]                  
Exchange of Class B common stock for Class A common stock 65,477   50,000 18,000          
Silvercrest L.P                  
Class Of Stock [Line Items]                  
Accrued partner incentive allocations           $ 5,022 $ 4,622 $ 14,123 $ 13,062