Postretirement Benefits - Schedule of Net Benefit (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 3	$ 5	$ 6
Interest on obligations	29	35	59	71
Amortization of cumulative loss	26	24	52	49
Amortization of cumulative loss	0	0	0	0
Contractual termination benefits	2	(1)	2	(1)
Premiums on pension insurance	4	4	8	5
Expected return on assets	(42)	(48)	(84)	(97)
Net postretirement benefits expense	22	17	42	33
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	3	3
Interest on obligations	15	18	30	36
Amortization of cumulative loss	8	9	16	19
Amortization of cumulative loss	(1)	(1)	(1)	(2)
Contractual termination benefits	0	(1)	0	(1)
Premiums on pension insurance	0	0	0	0
Expected return on assets	(7)	(8)	(13)	(15)
Net postretirement benefits expense	$ 17	$ 19	$ 35	$ 40