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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 337	$ 249	$ 1,012	$ 748
Interest cost	362	353	1,087	1,058
Expected return on assets	(537)	(493)	(1,611)	(1,478)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	44	43	130	130
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	206	152	618	458
U.S. Postretirement Medical Benefits
Net Periodic Cost:
Service cost	20	23	72	67
Interest cost	46	52	139	156
Expected return on assets	(8)	(4)	(25)	(13)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	1	1	3	3
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	59	72	189	213
International Pension Benefits
Net Periodic Cost:
Service cost	11	12	37	41
Interest cost	11	10	33	31
Expected return on assets	(14)	(11)	(42)	(35)
Amortization of:
Transition obligation	0	0	0	0
Other net (gain) loss	0	0	0	0
Prior service cost	0	1	0	1
Actuarial (gain) loss	0	0	0	0
Net periodic benefit cost	$ 8	$ 12	$ 28	$ 38