Postretirement Benefits - Summary of Changes in the Defined Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost Recognized	$ 8	$ 8	$ 15	$ 17
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	3	3	5	6
Interest on obligations	29	35	59	71
Actuarial loss (gain)	(9)		(18)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions	21	32	40	62
Health and Life Insurance Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	2	2	3	3
Interest on obligations	15	$ 18	30	$ 36
Actuarial loss (gain)	$ (4)		$ (8)