Postretirement Benefits - Schedule of Net Benefit (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned during the period	$ 2	$ 2	$ 4	$ 4
Interest on obligation	13	21	27	42
Amortization of cumulative loss (gain)	27	24	54	49
Contractual termination benefits	0	0	9	0
Premiums on pension insurance	2	3	5	6
Expected return on assets	(33)	(36)	(66)	(72)
Net periodic benefit expense (income)	11	14	33	29
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned during the period	1	1	1	2
Interest on obligation	2	7	5	14
Amortization of cumulative loss (gain)	(10)	0	(20)	0
Contractual termination benefits	0	0	3	0
Premiums on pension insurance	0	0	0	0
Expected return on assets	(4)	(5)	(8)	(10)
Net periodic benefit expense (income)	$ (11)	$ 3	$ (19)	$ 6