Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail)
12 Months Ended
Dec. 31, 2020
USD ($)
Office
Segment
Dec. 31, 2019
USD ($)
Office
Dec. 31, 2018
USD ($)
Office
Jan. 01, 2020
USD ($)
Dec. 31, 2017
USD ($)
Accounting Policies [Line Items]          
Commission's receivable settled period 10 days        
Number of offices | Office 84        
Advertising Costs $ 586,000 $ 889,000 $ 1,100,000    
Income tax benefit realized, percentage 50.00%        
Property and equipment, amortization method straight-line        
Number of reporting units | Segment 1        
Finite-lived intangible asset, amortization method straight-line        
Cumulative effect adjustment, net $ (546,836,000) (494,907,000) $ (409,574,000)   $ (314,888,000)
Line of credit 0        
Credit Agreement [Member]          
Accounting Policies [Line Items]          
Line of credit $ 0        
Cumulative Effect, Period of Adoption, Adjustment [Member]          
Accounting Policies [Line Items]          
Cumulative effect adjustment, net   $ 33,000     $ 0
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    
Transaction Risk [Member]          
Accounting Policies [Line Items]          
Concentration risk percentage 0.00% 0.00% 0.00%    
Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]          
Accounting Policies [Line Items]          
Cumulative effect adjustment, net       $ 33,000  
Minimum [Member]          
Accounting Policies [Line Items]          
Property and equipment, estimated useful lives 3 years        
Finite-lived intangible asset, useful life 1 year        
Minimum [Member] | Advances To Investment Sales And Financing Professionals [Member]          
Accounting Policies [Line Items]          
Advances to Investment Sales and Financing Professionals, Repayment Term 5 years        
Minimum [Member] | Loan To Investment Sales and Financing Professionals [Member]          
Accounting Policies [Line Items]          
Loans to Investment Sales and Financing Professionals, Repayment Term 1 year        
Maximum [Member]          
Accounting Policies [Line Items]          
Property and equipment, estimated useful lives 7 years        
Finite-lived intangible asset, useful life 7 years        
Maximum [Member] | Advances To Investment Sales And Financing Professionals [Member]          
Accounting Policies [Line Items]          
Advances to Investment Sales and Financing Professionals, Repayment Term 10 years        
Maximum [Member] | Loan To Investment Sales and Financing Professionals [Member]          
Accounting Policies [Line Items]          
Loans to Investment Sales and Financing Professionals, Repayment Term 7 years        
Maximum [Member] | Geographic Concentration Risk [Member] | Total revenues [Member] | CANADA [Member]          
Accounting Policies [Line Items]          
Concentration risk percentage 2.00% 1.00% 1.00%    
Capitalization of Internal Labor [Member]          
Accounting Policies [Line Items]          
Property and equipment, estimated useful lives 5 years