Variable Interest Entities (Investments in VIEs That Are Not Consolidated - Narrative) (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - USD ($) $ in Millions	Apr. 30, 2020	Oct. 31, 2019
Non-Consolidated CLO Entities [Abstract]
Total collateral management fees receivable held by the Company in non-consolidated entities	$ 0.1	$ 0.1
Total investments in CLO entities that the Company holds a variable interest in but is not deemed to be a primary beneficiary	1.4	1.4
Total assets in sponsored privately offered equity funds	26,900.0	26,300.0
Total investments in the privately offered equity funds entities that the Company holds a variable interest in but is not deemed to be a primary beneficiary	0.5	0.5
Total investment advisory fees receivable from the privately offered equity funds that the Company holds a variable interest in but is not deemed to be a primary beneficiary	1.3	1.3
Variable interest investment in private equity partnership that is not consolidated	$ 3.3	$ 3.5