Related Party Transactions (Details) (USD $)
3 Months Ended 6 Months Ended
Apr. 30, 2013
Apr. 30, 2012
Apr. 30, 2013
Apr. 30, 2012
Oct. 31, 2012
Sponsored Funds [Abstract]          
Investment advisory and administrative fees $ 201,790,000 $ 188,669,000 $ 393,982,000 $ 372,153,000  
Distribution fees 19,845,000 20,298,000 39,918,000 40,775,000  
Service fees 31,132,000 32,065,000 62,262,000 64,364,000  
Shareholder services fees 548,000 630,000 1,088,000 1,227,000  
Other revenue 268,000   403,000    
Total 253,583,000 241,662,000 497,653,000 478,519,000  
Investment advisory fees waived by the Company 1,600,000 2,100,000 4,400,000 4,500,000  
Proceeds from sales 18,474,000 32,804,000 39,290,000 40,006,000  
Net realized gains 342,000 61,000 5,251,000 124,000  
Related party expenses 5,600,000 4,300,000 10,700,000 8,700,000  
Related party accounts receivable 87,700,000   87,700,000   84,400,000
Employee Loan Program          
Maximum loan amount available under the plan $ 10,000,000   $ 10,000,000    
Minimum fixed borrowing rate under the plan     0.90%    
Maximum fixed borrowing rate under the plan     5.00%