Financial Instruments - Schedule of Pre-Tax Effect of Derivative Instruments and Related Hedged Items in a Fair Value Hedging Relationship (Details) - Interest and other, net - Interest rate contracts - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Oct. 31, 2020	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income/ (expense) line items in the statement of financial performance in which the effects of fair value hedges are recorded		$ (231)	$ (1,354)	$ (818)
Gain/ (loss) recognized in earnings on derivative instrument	$ 6		27	(11)
(Loss)/ gain recognized in earnings on hedged item		$ (6)	$ (27)	$ 11