Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Description of Business and Basis of Presentation - Additional Information (Detail)
 3 Months Ended
Jan. 01, 2017
USD ($)
Mar. 31, 2017
USD ($)
Office
Mar. 31, 2016
Office
Dec. 31, 2016
USD ($)
Class of Stock [Line Items]        
Number of offices in the United States and Canada | Office   80    
Formation date   2013-06    
Percentage of common stock distributed   80.00%    
Commission's receivable settled period   10 days    
Marketable securities, available for sale   $ 123,383,000   $ 104,929,000
IPO MMI [Member]        
Class of Stock [Line Items]        
IPO completion date   Oct. 30, 2013    
Accounting Standards Update 2016-02 [Member]        
Class of Stock [Line Items]        
Operating lease obligations   $ 86,300,000    
Marketable securities, available for sale   123,400,000    
Accounting Standards Update 2016-09 [Member]        
Class of Stock [Line Items]        
Cumulative effect adjustments, net of tax $ 52,000      
Accounting Standards Update 2016-13 [Member]        
Class of Stock [Line Items]        
Impairment write-downs marketable securities, available for sale   $ 0    
Geographic Concentration Risk [Member] | Total revenues [Member]        
Class of Stock [Line Items]        
Concentration risk percentage   10.00% 10.00%  
Number of offices | Office   0 0  
Customer Concentration Risk [Member] | Total revenues [Member]        
Class of Stock [Line Items]        
Concentration risk percentage   10.00% 10.00%  
Customer Concentration Risk [Member] | Commissions receivable [Member]        
Class of Stock [Line Items]        
Concentration risk percentage   10.00% 10.00%  
International Revenues [Member] | Geographic Concentration Risk [Member] | Total revenues [Member] | Maximum [Member]        
Class of Stock [Line Items]        
Concentration risk percentage   1.00%