Annual report pursuant to Section 13 and 15(d)

Accounting Policies - Additional Information (Detail)

v3.3.1.900
Accounting Policies - Additional Information (Detail)
 10 Months Ended 12 Months Ended
Oct. 31, 2013
Oct. 31, 2013
Dec. 31, 2015
USD ($)
Financial_Institutions
Segments
Fund
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Accounting Policies [Line Items]          
Number of money market fund | Fund     1    
Number of financial institutions | Financial_Institutions     4    
Sweep arrangement termination date     Jun. 30, 2013    
Allowance for commissions receivable     $ 0 $ 0  
Other-than-temporary impairment     0 0  
Advertising expense     $ 1,100,000 965,000 $ 975,000
Income tax benefit realized, percentage     50.00%    
Uncertain tax positions     $ 0 0  
Tax sharing agreement termination date     Oct. 31, 2013    
Payment of dividend         $ 37,681,000
Commission's receivable settled period     10 days    
Number of reportable segments | Segments     1    
Current deferred taxes reclassified as non-current deferred taxes       $ 13,600,000  
Operating lease obligations     $ 79,752,000    
Employee Stock Purchase Plan [Member]          
Accounting Policies [Line Items]          
Length of purchase intervals     6 months    
Expected dividend yield     0.00%    
Forfeiture rate     0.00%    
Payment of dividend     $ 0    
Customer Concentration Risk [Member] | Total revenues [Member]          
Accounting Policies [Line Items]          
Concentration of credit risk percentage     10.00% 10.00%  
Customer Concentration Risk [Member] | Commissions receivable [Member]          
Accounting Policies [Line Items]          
Concentration of credit risk percentage     10.00% 10.00%  
Tax-sharing agreement [Member]          
Accounting Policies [Line Items]          
Effective income tax rate, pre-IPO 43.50%     43.50% 43.50%
Tax sharing agreement termination date     Oct. 31, 2013    
Maximum [Member]          
Accounting Policies [Line Items]          
Property and equipment, estimated useful lives     7 years    
Maximum [Member] | Pre-IPO [Member]          
Accounting Policies [Line Items]          
Vesting period   5 years      
Minimum [Member]          
Accounting Policies [Line Items]          
Property and equipment, estimated useful lives     3 years    
Minimum [Member] | Pre-IPO [Member]          
Accounting Policies [Line Items]          
Vesting period   3 years