Postretirement Benefits - Schedule of Net Benefit (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2017	Apr. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost Recognized	$ 9	$ 8	$ 16	$ 15
Employer contributions	24	21	46	40
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	(2)	(3)	(4)	(5)
Interest on obligations	26	29	53	59
Amortization of cumulative loss	30	26	59	52
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	0	0
Contractual termination benefits	0	2	1	2
Premiums on pension insurance	4	4	8	8
Expected return on assets	(39)	(42)	(79)	(84)
Net postretirement benefits expense	23	22	46	42
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	(2)	(2)	(3)	(3)
Interest on obligations	12	15	24	30
Amortization of cumulative loss	5	8	11	16
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	(1)	0	(1)
Contractual termination benefits	0	0	0	0
Premiums on pension insurance	0	0	0	0
Expected return on assets	(6)	(7)	(12)	(13)
Net postretirement benefits expense	$ 13	$ 17	$ 26	$ 35