Pension and Other Benefit Programs - Benefit Obligations, Assets, Funded Status and Balance Sheet Impacts Associated with Pension and Postretirement Medical Benefit Plans based upon Actuarial Valuations (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Oct. 03, 2015
Fair value of plans' assets
Beginning fair value	$ 11,015
Contributions	1,400
Ending fair value	13,021	$ 11,015
Amounts recognized in the balance sheet
Non-current liabilities	(3,281)	(5,184)
Net balance sheet liability	(3,257)
Pension Plans
Projected benefit obligations
Beginning obligations	(14,480)	(12,379)
Service cost	(368)	(318)	$ (332)
Interest cost	(447)	(458)	(521)
Actuarial gain / (loss)	343	(1,769)
Plan amendments and other	(22)	8
Benefits paid	442	436
Ending obligations	(14,532)	(14,480)	(12,379)
Fair value of plans' assets
Beginning fair value	10,401	9,415
Actual return on plan assets	1,056	624
Contributions	1,348	839
Benefits paid	(442)	(436)
Expenses and other	(38)	(41)
Ending fair value	12,325	10,401	9,415
Underfunded status of the plans	(2,207)	(4,079)
Amounts recognized in the balance sheet
Non-current assets	70	0
Current liabilities	(46)	(40)
Non-current liabilities	(2,231)	(4,039)
Net balance sheet liability	(2,207)	(4,079)
Postretirement Medical Plans
Projected benefit obligations
Beginning obligations	(1,759)	(1,590)
Service cost	(11)	(11)	(14)
Interest cost	(56)	(61)	(68)
Actuarial gain / (loss)	42	(142)
Plan amendments and other	(9)	(9)
Benefits paid	47	54
Ending obligations	(1,746)	(1,759)	(1,590)
Fair value of plans' assets
Beginning fair value	614	568
Actual return on plan assets	61	34
Contributions	61	61
Benefits paid	(47)	(54)
Expenses and other	(7)	(5)
Ending fair value	696	614	$ 568
Underfunded status of the plans	(1,050)	(1,145)
Amounts recognized in the balance sheet
Non-current assets	0	0
Current liabilities	0	0
Non-current liabilities	(1,050)	(1,145)
Net balance sheet liability	$ (1,050)	$ (1,145)