Variable Interest Entities (Investments in VIEs That Are Consolidated - Narrative) (Details)			3 Months Ended	12 Months Ended
	May 15, 2019 USD ($)	May 01, 2019 USD ($)	Jan. 31, 2019 USD ($)	Oct. 31, 2019 USD ($) Number	Oct. 31, 2018 USD ($) Number
Variable Interest Entity [Line Items]
Number Of Nonrecourse CLO Entities | Number				4	3
Eaton Vance CLO 2015-1 [Member]
Variable Interest Entity [Line Items]
Percentage of equity interest in CLO entity				5.00%
Percentage of equity interest purchased in CLO entity					100.00%
Amount paid to acquire equity interest in CLO entity					$ 26,700,000
Percentage of equity interest in CLO entity sold					95.00%
Proceeds from sale of equity interest in CLO entity					$ 24,700,000
Loss on disposal of equity interest in CLO entity					600,000
Senior debt tranches of the CLO entity held by the Company					28,100,000
Proceeds from sale of investments in senior debt tranches					28,000,000.0
Loss on disposal of investments in senior debt tranches					$ 100,000
Eaton Vance CLO 2014-1 [Member]
Variable Interest Entity [Line Items]
Distribution from CLO entity			$ 1,900,000
Eaton Vance CLO 2013-1 [Member]
Variable Interest Entity [Line Items]
Payment to acquire subordinated notes		$ 25,400,000
Company's subordinated interest in non-consolidated CLO entities		100.00%			100.00%
Total investments held by the Company in non-consolidated entities					$ 1,400,000
Eaton Vance CLO 2019-1 [Member]
Variable Interest Entity [Line Items]
Contribution to a CLO entity				$ 40,000,000.0
Line of Credit Facility, Maximum Borrowing Capacity				$ 160,000,000.0
Percentage of equity interest purchased in CLO entity	100.00%
Distribution from CLO entity	$ 40,000,000.0
Payment to acquire subordinated notes	$ 28,900,000
Eaton Vance CLO 2018-1 [Member]
Variable Interest Entity [Line Items]
Percentage of equity interest in CLO entity				93.00%	93.00%
Eaton Vance CLO 2014-1R [Member]
Variable Interest Entity [Line Items]
Percentage of equity interest in CLO entity				100.00%	100.00%
Privately Offered Equity Fund [Member] | Promissory Note [Member]
Variable Interest Entity [Line Items]
Contribution to a CLO entity				$ 10,000
Line of Credit Facility, Maximum Borrowing Capacity					$ 25,000,000.0
Line of credit, amount outstanding					3,700,000
Total contribution to a CLO				20,000	10,000
Consolidated Securitized CLO Entities [Member]
Variable Interest Entity [Line Items]
Total variable interest in consolidated securitized CLO entities equal to the net carrying amount				$ 112,796,000	$ 68,173,000