Pension and Other Benefit Programs - Accumulated Other Comprehensive Loss, Before Tax, not yet Recognized in Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Oct. 01, 2016
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	$ (65)
Net actuarial loss	(4,772)
Total amounts included in AOCI	(4,837)
Prepaid / (accrued) pension cost	1,580
Net balance sheet liability	(3,257)
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	(65)
Net actuarial loss	(4,578)
Total amounts included in AOCI	(4,643)
Prepaid / (accrued) pension cost	2,436
Net balance sheet liability	(2,207)	$ (4,079)
Postretirement Medical Plans
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	0
Net actuarial loss	(194)
Total amounts included in AOCI	(194)
Prepaid / (accrued) pension cost	(856)
Net balance sheet liability	$ (1,050)	$ (1,145)