Postretirement Benefits - Schedule of Net Benefit (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 2	$ 6	$ 6
Interest on obligations	35	40	71	79
Amortization of cumulative loss	24	23	49	47
Amortization of cumulative loss	0	0	0	0
Contractual termination benefits	(1)	0	(1)	0
Premiums on pension insurance	4	0	5	0
Expected return on assets	(48)	(48)	(97)	(96)
Net postretirement benefits expense	17	17	33	36
Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	3	2
Interest on obligations	18	17	36	34
Amortization of cumulative loss	9	4	19	8
Amortization of cumulative loss	(1)	(1)	(2)	(2)
Contractual termination benefits	(1)	0	(1)	0
Premiums on pension insurance	0	0	0	0
Expected return on assets	(8)	(8)	(15)	(16)
Net postretirement benefits expense	$ 19	$ 13	$ 40	$ 26