Quarterly report pursuant to Section 13 or 15(d)

Description of Business and Basis of Presentation - Additional Information (Detail)

v3.10.0.1
Description of Business and Basis of Presentation - Additional Information (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Transactions
Office
Sep. 30, 2017
Transactions
Office
Sep. 30, 2018
Transactions
Office
Sep. 30, 2017
Transactions
Office
Class of Stock [Line Items]        
Number of offices | Office     79  
Formation date     2013-06  
Percentage of common stock distributed     80.00%  
Commission's receivable settled period 10 days      
Customer Concentration Risk [Member] | Total revenues [Member]        
Class of Stock [Line Items]        
Concentration risk percentage 10.00% 10.00% 10.00% 10.00%
Number of transactions | Transactions 0 0 0 0
Customer Concentration Risk [Member] | Commissions receivable [Member]        
Class of Stock [Line Items]        
Concentration risk percentage 10.00% 10.00% 10.00% 10.00%
Number of transactions | Transactions 1 1 1 1
Geographic Concentration Risk [Member] | Total revenues [Member]        
Class of Stock [Line Items]        
Number of offices | Office 0 0 0 0
Concentration risk percentage 10.00% 10.00% 10.00% 10.00%
Geographic Concentration Risk [Member] | Total revenues [Member] | International Revenues [Member] | Maximum [Member]        
Class of Stock [Line Items]        
Concentration risk percentage 1.00% 1.00% 1.00% 1.00%
IPO MMI [Member]        
Class of Stock [Line Items]        
IPO completion date     Oct. 30, 2013