Investments (Details) - USD ($) $ in Thousands	Apr. 30, 2017	Oct. 31, 2016
Schedule Of Investments [Line Items]
Investments	$ 750,121	$ 589,773
Total investment securities, trading	579,439	413,541
Equity Securities [Member]
Schedule Of Investments [Line Items]
Total investment securities, trading	213,600	136,031
Debt Securities [Member]
Schedule Of Investments [Line Items]
Total investment securities, trading	299,248	191,688
Trading Account Assets [Member]
Schedule Of Investments [Line Items]
Total investment securities, trading	579,439	413,541
Short Term Debt Securities[Member] | Trading Account Assets [Member]
Schedule Of Investments [Line Items]
Investments	66,591	85,822
Consolidated Sponsored Funds [Member] | Trading Account Assets [Member]
Schedule Of Investments [Line Items]
Investments	424,440	248,036
Separately Managed Accounts [Member] | Trading Account Assets [Member]
Schedule Of Investments [Line Items]
Investments	88,408	79,683
Available-for-sale Securities [Member]
Schedule Of Investments [Line Items]
Investments	10,712	13,312
Investments in non-consolidated CLO entities [Member]
Schedule Of Investments [Line Items]
Investments	2,928	3,837
Equity Method Investments [Member]
Schedule Of Investments [Line Items]
Investments	137,911	139,929
Investments, Other [Member]
Schedule Of Investments [Line Items]
Investments	$ 19,131	$ 19,154