Investments (Details) (USD $)
In Thousands, unless otherwise specified
Apr. 30, 2013
Oct. 31, 2012
Schedule Of Investments [Line Items]    
Investments $ 542,058 $ 486,933
Total investment securities, trading 285,021 190,253
Equity Securities [Member]
   
Schedule Of Investments [Line Items]    
Total investment securities, trading 186,796 119,448
Debt Securities [Member]
   
Schedule Of Investments [Line Items]    
Total investment securities, trading 98,225 70,805
Categories of Investments, Marketable Securities, Trading Securities [Member]
   
Schedule Of Investments [Line Items]    
Total investment securities, trading 285,021 190,253
Consolidated Sponsored Funds [Member] | Categories of Investments, Marketable Securities, Trading Securities [Member]
   
Schedule Of Investments [Line Items]    
Investments 243,657 157,405
Separately Managed Accounts [Member] | Categories of Investments, Marketable Securities, Trading Securities [Member]
   
Schedule Of Investments [Line Items]    
Investments 41,364 32,848
Available-for-sale Securities [Member]
   
Schedule Of Investments [Line Items]    
Investments 19,770 31,148
Collateralized Loan Obligations [Member]
   
Schedule Of Investments [Line Items]    
Investments 314 350
Equity Method Investments [Member]
   
Schedule Of Investments [Line Items]    
Investments 229,422 257,652
Cost Method Investments [Member]
   
Schedule Of Investments [Line Items]    
Investments $ 7,531 $ 7,530