Pension and Other Benefit Plans - Changes in Projected Benefit Obligation, Plan Assets and Funded Status of Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts Recognized in Balance Sheet
Postretirement Benefits	$ (1,082)	$ (1,495)
US Plan Assets
Change in Projected Benefit Obligations
Projected benefit obligation at beginning of year	4,240	4,025
Service cost	57	62	$ 86
Interest cost	175	177	170
Actuarial (gains) losses	325	137
Benefits paid	(194)	(183)
Other		22
Projected benefit obligation at end of year	4,603	4,240	4,025
Change in Plan Assets
Plan assets at fair value at beginning of year	3,625	3,467
Actual return on plan assets	622	320
Company contributions	5	4
Benefits paid	(194)	(183)
Other		17
Plan assets at fair value at end of year	4,058	3,625	3,467
Unfunded Liability	(545)	(615)
Amounts Recognized in Balance Sheet
Postretirement Benefits	(545)	(615)
Total of post retirement benefits	(545)	(615)
Amounts Recognized in Accumulated Other Comprehensive Loss
Actuarial losses	887	982
Prior service cost	30	42
Total amount recognized in accumulated other comprehensive income	917	1,024
Accumulated benefit obligation	4,347	3,999
International
Change in Projected Benefit Obligations
Projected benefit obligation at beginning of year	7,793	7,340
Service cost	95	110	167
Interest cost	306	311	297
Contribution by plan participants	88	117
Actuarial (gains) losses	616	477
Currency effect	147	(290)
Benefits paid	(293)	(272)
Projected benefit obligation at end of year	8,752	7,793	7,340
Change in Plan Assets
Plan assets at fair value at beginning of year	7,194	6,832
Actual return on plan assets	1,216	715
Currency effect	161	(318)
Company contributions	88	130
Contributions by plan participants	88	117
Benefits paid	(293)	(272)
Other	53	(10)
Plan assets at fair value at end of year	8,507	7,194	$ 6,832
Unfunded Liability	(245)	(599)
Amounts Recognized in Balance Sheet
Postretirement Benefits	(418)	(724)
Other Assets	173	125
Total of post retirement benefits	(245)	(599)
Amounts Recognized in Accumulated Other Comprehensive Loss
Actuarial losses	1,419	1,644
Prior service cost	17	114
Total amount recognized in accumulated other comprehensive income	1,436	1,758
Accumulated benefit obligation	$ 8,400	$ 7,454