Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 799,384	$ 557,668
Total cash, cash equivalents and restricted cash presented in the Consolidated Statement of Cash Flows	936,666	653,345	$ 866,075	$ 649,863
Consolidated Sponsored Funds Included In Investments [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted Cash	31,165	37,905
Cash In Assets Of Consolidated CLO Entities [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted Cash	91,795	48,704
Cash Included In Other Assets [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted Cash	$ 14,322	$ 9,068