Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	$ (25)	$ 0	$ (50)	$ 0
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	83	87	166	175
Interest costs	144	122	289	245
Expected return on plan assets	(240)	(227)	(479)	(452)
Amortization of prior-year service costs	4	5	7	8
Recognized net actuarial loss	67	88	131	175
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	(25)	(12)	(52)	(24)
Net periodic benefit cost	58	75	114	151
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Service costs	2	2	4	5
Interest costs	17	15	33	30
Expected return on plan assets	(14)	(13)	(28)	(26)
Amortization of prior-year service costs	0	0	0	0
Recognized net actuarial loss	0	4	0	7
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	3	6	5	11
Net periodic benefit cost	$ 5	$ 8	$ 9	$ 16