Postretirement Benefits - Schedule of Net Benefit (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019	Oct. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 7
Employer contributions					$ 5
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	$ 1	$ 6	$ 5
Interest on obligations	21	30	63	92
Amortization of cumulative loss	24	23	73	70
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	7	0	7	142
Premiums on pension insurance	3	3	9	7
Expected return on assets	(36)	(35)	(108)	(108)
Net postretirement benefits expense	21	22	50	208
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	3	3
Interest on obligations	7	12	21	36
Amortization of cumulative loss	0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	0	0
Premiums on pension insurance	0	0	0	0
Expected return on assets	(5)	(5)	(15)	(16)
Net postretirement benefits expense	$ 3	$ 8	$ 9	$ 23