Investments (Summary of net gains (losses) on securities held at fair value) (Details) - USD ($) $ in Thousands	12 Months Ended
Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Investments [Abstract]
Realized gains (losses) on securities sold	$ (6,223)	$ (505)	$ 6,951
Unrealized gains (losses) on investments held at fair value	(13,580)	20,416	(22,814)
Net gains (losses) on investments held at fair value	$ (19,803)	$ 19,911	$ (15,863)

Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(9)(a))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration