Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 284	$ 337	$ 853	$ 1,012
Interest cost	401	362	1,203	1,087
Expected return on assets	(564)	(537)	(1,693)	(1,611)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	42	44	127	130
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	163	206	490	618
U.S. Postretirement Medical Benefits
Net Periodic Cost:
Service cost	12	20	51	72
Interest cost	33	46	119	139
Expected return on assets	(6)	(8)	(18)	(25)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	1	1	(2)	3
Actuarial (gain) loss	0	0	746	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0		320
Net periodic benefit cost	40	59	1,216	189
International Pension Benefits
Net Periodic Cost:
Service cost	10	11	37	37
Interest cost	12	11	38	33
Expected return on assets	(15)	(14)	(45)	(42)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	1	0	(2)	0
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	$ 8	$ 8	$ 28	$ 28