Variable Interest Entities Investments in VIEs That Are Not Consolidated (Details) - USD ($) $ in Millions	Jan. 31, 2018	Oct. 31, 2017
Non-Consolidated CLO Entities [Abstract]
Total collateral management fees receivable held by the Company in non-consolidated entities	$ 0.5	$ 0.4
Other Entities [Abstract]
Total assets of the privately offered equity funds that the Company holds a variable interest in but is not deemed to be a primary beneficiary	20,400.0	18,100.0
Total investments of the privately offered equity funds that the Company holds a variable interest in but is not deemed to be a primary beneficiary	2.9	2.7
Total collateral management fees receivable of the privately offered equity funds that the Company holds a variable interest in but is not deemed to be a primary beneficiary	1.3	1.1
Variable interest investment in private equity partnership that is not consolidated	$ 3.2	$ 2.9