Investments (Summary of net gains (losses) on securities held at fair value) (Details) - USD ($) $ in Thousands	3 Months Ended
Jan. 31, 2020	Jan. 31, 2019
Investments [Abstract]
Realized gains (losses) on securities sold	$ 3,875	$ (4,395)
Unrealized gains (losses) on investments held at fair value	7,637	3,305
Net gains (losses) on investments held at fair value	$ 11,512	$ (1,090)

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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration