Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 353	$ 382	$ 1,059	$ 1,145
Interest cost	457	423	1,371	1,270
Expected return on assets	(629)	(622)	(1,887)	(1,866)
Amortization of:
Prior service cost	41	42	125	126
Net periodic benefit cost	222	225	668	675
U.S. Postretirement Medical Benefits
Net Periodic Cost:
Service cost	7	8	21	25
Interest cost	32	30	92	91
Expected return on assets	(2)	(5)	(4)	(13)
Amortization of:
Prior service cost	1	2	3	4
Net periodic benefit cost	38	35	112	107
International Pension Benefits
Net Periodic Cost:
Service cost	12	12	37	37
Interest cost	10	11	31	33
Expected return on assets	(15)	(15)	(44)	(46)
Amortization of:
Prior service cost	0	0	0	1
Net periodic benefit cost	$ 7	$ 8	$ 24	$ 25