Annual report pursuant to Section 13 and 15(d)

Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail)

v3.19.3.a.u2
Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2019
USD ($)
Office
Segment
Dec. 31, 2018
USD ($)
Office
Dec. 31, 2017
USD ($)
Office
Jan. 01, 2019
USD ($)
Accounting Policies [Line Items]        
Commission's receivable settled period 10 days      
Number of offices | Office 82      
Operating lease right-of-use assets $ 90,535,000 $ 0    
Operating lease liabilities 80,917,000      
Prepaid Rent Reclassified to Other Assets, Current 6,067,000 6,368,000    
Advertising Costs $ 889,000 1,100,000 $ 824,000  
Income tax benefit realized, percentage 50.00%      
Property and equipment, amortization method straight-line      
Allowance for commissions receivable $ 0 $ 0    
Number of reporting units | Segment 1      
Finite-lived intangible asset, amortization method straight-line      
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 risk percentage 10.00% 10.00% 10.00%  
Customer Concentration Risk [Member] | Commissions receivable [Member]        
Accounting Policies [Line Items]        
Concentration risk percentage 10.00% 10.00% 10.00%  
Geographic Concentration Risk [Member] | Total revenues [Member]        
Accounting Policies [Line Items]        
Concentration risk percentage 10.00% 10.00% 10.00%  
Number of offices | Office 0 0 0  
Accounting Standards Update 2016-02 [Member]        
Accounting Policies [Line Items]        
Operating lease right-of-use assets       $ 76,700,000
Operating lease liabilities       76,700,000
Prepaid Rent Reclassified to Other Assets, Current       462,000,000
Accounting Standards Update 2016-02 [Member] | Deferred rent reclassified to Operating Lease ROU Asset [Member]        
Accounting Policies [Line Items]        
Operating lease right-of-use assets       5,600,000
Accounting Standards Update 2016-02 [Member] | Prepaid rent reclassified to Operating Lease ROU Asset [Member]        
Accounting Policies [Line Items]        
Operating lease right-of-use assets       $ 13,400,000
Maximum [Member]        
Accounting Policies [Line Items]        
Property and equipment, estimated useful lives 7 years      
Finite-lived intangible asset, useful life 6 years      
Maximum [Member] | Geographic Concentration Risk [Member] | Total revenues [Member] | International Revenues [Member]        
Accounting Policies [Line Items]        
Concentration risk percentage 1.00% 1.00% 1.00%  
Minimum [Member]        
Accounting Policies [Line Items]        
Property and equipment, estimated useful lives 3 years      
Finite-lived intangible asset, useful life 1 year      
Capitalization of Internal Labor [Member]        
Accounting Policies [Line Items]        
Property and equipment, estimated useful lives 5 years