Investments (Summary of Investments) (Details) - USD ($) $ in Thousands	Oct. 31, 2018	Oct. 31, 2017
Marketable Securities [Line Items]
Total investment securities, trading	$ 903,023	$ 708,376
Investment securities, available-for-sale	10,329	22,465
Investments in non-consolidated CLO entities	2,895	3,609
Investments in equity method investees	141,506	144,911
Investments, other	20,874	18,831
Total investments	1,078,627	898,192
Short-term Debt Securities [Member]
Marketable Securities [Line Items]
Total investment securities, trading	273,320	213,537
Consolidated Sponsored Funds [Member]
Marketable Securities [Line Items]
Total investment securities, trading	540,582	401,726
Separately Managed Accounts [Member]
Marketable Securities [Line Items]
Total investment securities, trading	$ 89,121	$ 93,113