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 6 Months Ended
Jun. 30, 2015
May. 31, 2015
Mar. 31, 2015
Feb. 28, 2015
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Class Of Stock [Line Items]                
Partnership distributions, amount         $ 2,883 $ 2,646 $ 4,125 $ 3,995
Distributions of partner incentive allocations of net income             $ 18,568 14,206
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             (68,000)  
Class B Common Stock | Jamison Acquisition                
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   50,000 18,000          
Silvercrest L.P                
Class Of Stock [Line Items]                
Accrued partner incentive allocations         $ 4,860 $ 4,326 $ 9,101 $ 8,440