Postretirement Benefits - Schedule of Net Benefit (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 8	$ 7	$ 28	$ 25
Employer contributions	9	25	140	78
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	5	5
Interest on obligations	30	27	92	81
Amortization of cumulative loss	23	26	70	79
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	142	9
Premiums on pension insurance	3	1	7	3
Expected return on assets	(35)	(40)	(108)	(121)
Net postretirement benefits expense	22	15	208	56
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	3	3
Interest on obligations	12	10	36	32
Amortization of cumulative loss	0	3	0	7
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)	(16)	(17)
Net postretirement benefits expense	$ 8	$ 9	$ 23	$ 25