Investments In Affiliates (Details) (USD $)
12 Months Ended
Oct. 31, 2011
Oct. 31, 2010
Lloyd George Management Limited [Member]
   
Schedule Of Equity Method Investments [Line Items]    
Equity method investment aggregate cost   $ 8,000,000
Realized gains 5,500,000  
Private Equity Partnership [Member]
   
Schedule Of Equity Method Investments [Line Items]    
Equity method investment ownership percentage 7.00%  
Equity method investment aggregate cost 18,400,000 12,800,000
Eaton Vance Parametric Option Absolute Return Strategy Fund[ Member]
   
Schedule Of Equity Method Investments [Line Items]    
Equity method investment ownership percentage 27.00%  
Equity method investment aggregate cost 19,298,000  
Eaton Vance Global Macro Absolute Return Advantage Fund [Member]
   
Schedule Of Equity Method Investments [Line Items]    
Equity method investment ownership percentage   33.00%
Equity method investment aggregate cost   30,259,000
Eaton Vance Parametric Structured Commodity Strategy Fund [Member]
   
Schedule Of Equity Method Investments [Line Items]    
Equity method investment ownership percentage 47.00%  
Equity method investment aggregate cost $ 9,190,000