Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Nov. 01, 2018	Oct. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component		$ 31
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ 11	2
Defined Contribution Plan, Administrative Expense	142	9
Liabilities	10,850		$ 11,074	$ 11,156
Employer contributions	131	21
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	9
Income Tax Expense (Benefit)	(19)	15
Liability, Defined Benefit Plan, Noncurrent	1,961			$ 2,097
Defined Contribution Plan, Cost	$ 8	$ 7