Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 381	$ 285	$ 763	$ 569
Interest cost	424	401	847	802
Expected return on assets	(622)	(565)	(1,244)	(1,129)
Amortization of:
Transition obligation	0	0	0	0
Prior service cost	42	43	84	85
Other net (gain) loss	0	0	0	0
Actuarial (gain) loss	0	0	0	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	0	0	0
Net periodic benefit cost	225	164	450	327
U.S. Postretirement Medical Benefits
Net Periodic Cost:
Service cost	8	18	17	39
Interest cost	30	34	61	86
Expected return on assets	(4)	(6)	(8)	(12)
Amortization of:
Transition obligation	0	0	0	0
Prior service cost	1	(4)	2	(3)
Other net (gain) loss	0	0	0	0
Actuarial (gain) loss	0	746	0	746
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	320	0	320
Net periodic benefit cost	35	1,108	72	1,176
International Pension Benefits
Net Periodic Cost:
Service cost	13	15	25	27
Interest cost	11	14	22	26
Expected return on assets	(16)	(15)	(31)	(30)
Amortization of:
Transition obligation	0	0	0	0
Prior service cost	1	(3)	1	(3)
Other net (gain) loss	0	0	0	0
Actuarial (gain) loss	0	0	0	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	0	0	0
Net periodic benefit cost	$ 9	$ 11	$ 17	$ 20