Postretirement Benefits - Schedule of Net Benefit (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 12	$ 11	$ 20	$ 18
Employer contributions	0	32	131	53
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	4	4
Interest on obligations	30	27	62	54
Amortization of cumulative loss	23	27	47	53
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	142	9
Premiums on pension insurance	3	0	4	2
Expected return on assets	(35)	(41)	(73)	(81)
Net postretirement benefits expense	23	15	186	41
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2	2
Interest on obligations	12	11	24	22
Amortization of cumulative loss	0	2	0	4
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	(6)	(6)	(11)	(12)
Net postretirement benefits expense	$ 7	$ 8	$ 15	$ 16