Investments (Summary of Investments) (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Oct. 31, 2019
Marketable Securities [Line Items]
Non-consolidated sponsored funds and other	$ 10,502	$ 10,329
Total investments held at fair value	934,346	898,908
Investments held at cost	20,904	20,904
Investments in non-consolidated CLO entities	1,399	1,417
Investments in equity method investees	138,454	139,510
Total investments	1,095,103	1,060,739
Debt Securities: Short-term [Member]
Marketable Securities [Line Items]
Total investment securities held at fair value	280,590	297,845
Debt and Equity Securities Held by Consolidated Sponsored Funds [Member]
Marketable Securities [Line Items]
Total investment securities held at fair value	563,742	514,072
Debt and Equity Securities Held in Separately Managed Accounts [Member]
Marketable Securities [Line Items]
Total investment securities held at fair value	$ 79,512	$ 76,662

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Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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