Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 337	$ 250	$ 675	$ 499
Interest cost	363	352	725	705
Expected return on assets	(537)	(493)	(1,074)	(985)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	43	44	86	87
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	206	153	412	306
U.S. Postretirement Medical Benefits
Net Periodic Cost:
Service cost	26	22	52	44
Interest cost	47	52	93	104
Expected return on assets	(9)	(5)	(17)	(9)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	1	1	2	2
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	65	70	130	141
International Pension Benefits
Net Periodic Cost:
Service cost	11	14	26	29
Interest cost	11	10	22	21
Expected return on assets	(14)	(12)	(28)	(24)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	0	0	0	0
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	$ 8	$ 12	$ 20	$ 26