Variable Interest Entities (Investments in vies that are consolidated - Narrative) (Details) $ in Thousands	12 Months Ended
	Oct. 31, 2020 USD ($) Number	Oct. 31, 2019 USD ($) Number	Oct. 31, 2018 USD ($)
Variable Interest Entity [Line Items]
Number of consolidated sponsored funds | Number	17	19
Number of nonrecourse CLO entities | Number	4	4
Total assets	$ 4,949,298	$ 4,253,629
Notes Payable [Member]
Variable Interest Entity [Line Items]
Prinicipal amount of debt issued	1,800,000
Notes Payable [Member] | Senior Secured Floating Rate Notes Payable [Member]
Variable Interest Entity [Line Items]
Prinicipal amount of debt issued	1,600,000
Notes Payable [Member] | Subordinated Notes [Member]
Variable Interest Entity [Line Items]
Prinicipal amount of debt issued	$ 162,100
Bank Loan Investments [Member]
Variable Interest Entity [Line Items]
Investment, variable rate spread	13.80%
Percent of collateral assets in default	0.80%
Maximum [Member] | Notes Payable [Member]
Variable Interest Entity [Line Items]
Debt instrument basis spread on variable rate	8.50%
Minimum [Member] | Notes Payable [Member]
Variable Interest Entity [Line Items]
Debt instrument basis spread on variable rate	0.70%
Consolidated Securitized CLO Entities [Member]
Variable Interest Entity [Line Items]
Total variable interest in consolidated securitized CLO entities equal to the net carrying amount	$ 85,665	112,796
Gains Losses Attributable to Company, Net, Consolidated Variable Interest Entity	(18,577)	$ 9,104	$ (1,532)
Consolidated Warehouse CLO Entities [Member]
Variable Interest Entity [Line Items]
Total variable interest in consolidated securitized CLO entities equal to the net carrying amount	$ 38,877