Fair Value - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Jul. 31, 2020	Apr. 30, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019	Oct. 31, 2019
Financial assets and liabilities measured at fair value on a recurring basis
Impairment of goodwill	$ 0		$ 0	$ 865	$ 0
HPC & MCS
Financial assets and liabilities measured at fair value on a recurring basis
Impairment of goodwill	865	$ 865		865
HPC & MCS | Level 3
Financial assets and liabilities measured at fair value on a recurring basis
Impairment of goodwill		$ 865
Fair Value
Financial assets and liabilities measured at fair value on a recurring basis
Fair value, short-term and long-term debt	20,600			20,600		$ 14,600
Reported Value Measurement [Member]
Financial assets and liabilities measured at fair value on a recurring basis
Fair value, short-term and long-term debt	$ 19,500			$ 19,500		$ 13,800