Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	$ (25)	$ 0
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	83	88
Interest costs	145	123
Expected return on plan assets	(239)	(225)
Amortization of prior-year service costs	3	3
Recognized net actuarial loss	64	87
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	(27)	(12)
Net periodic benefit cost	56	76
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	2	3
Interest costs	16	15
Expected return on plan assets	(14)	(13)
Amortization of prior-year service costs	0	0
Recognized net actuarial loss	0	3
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	2	5
Net periodic benefit cost	$ 4	$ 8