Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 389	$ 353	$ 779	$ 706
Interest cost	462	457	924	914
Expected return on assets	(712)	(629)	(1,424)	(1,258)
Amortization of:
Prior service cost	48	42	96	84
Net periodic benefit cost	187	223	375	446
U.S. Postretirement Medical Benefits
Net Periodic Cost:
Service cost	7	7	14	14
Interest cost	28	30	56	60
Expected return on assets	(1)	(1)	(3)	(2)
Amortization of:
Prior service cost	2	1	4	2
Net periodic benefit cost	36	37	71	74
International Pension Benefits
Net Periodic Cost:
Service cost	14	13	29	25
Interest cost	10	11	20	21
Expected return on assets	(16)	(15)	(32)	(29)
Amortization of:
Prior service cost	0	0	0	0
Net periodic benefit cost	$ 8	$ 9	$ 17	$ 17