Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Jan. 31, 2018	Jul. 31, 2017	Jan. 31, 2017	Jul. 31, 2014	Oct. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 21		$ 22
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	113
Defined Benefit Plan, Cost of Providing Special and Contractual Termination Benefits			1
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	2
Defined Contribution Plan, Administrative Expense	9
Income Tax Expense (Benefit)	15		4
Liability, Defined Benefit Plan, Noncurrent	2,467				$ 2,497
Defined Contribution Plan, Cost	$ 7		6
Chatham [Member] | Facility Closing [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Postemployment Benefits, Period Expense		$ 23	$ 6	$ 14
Liability, Defined Benefit Plan, Noncurrent		$ 66