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Significant Accounting Policies - Additional Information (Detail) (USD $)
 9 Months Ended
Sep. 30, 2013
Segment
Dec. 31, 2012
Business Organization And Significant Accounting Policies [Line Items]    
Number of business segment 1  
Allowance for doubtful accounts $ 0 $ 0
Period of variable incentive fees 5 years  
Advance commissions amortization period 12 months  
Class A [Member]
    
Business Organization And Significant Accounting Policies [Line Items]    
Rate of Administrative Service Fees 0.25%  
Class C [Member]
    
Business Organization And Significant Accounting Policies [Line Items]    
Rate of Administrative Service Fees 0.25%  
Class I [Member]
    
Business Organization And Significant Accounting Policies [Line Items]    
Rate of Administrative Service Fees 0.25%  
Class Y [Member]
    
Business Organization And Significant Accounting Policies [Line Items]    
Rate of Administrative Service Fees 0.10%