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, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Plan Assets
Benefits paid	$ (257)
Amounts Recognized in Balance Sheet
Postretirement Benefits	(1,049)	$ (967)
US
Change in Projected Benefit Obligations
Projected benefit obligation at beginning of year	4,593	4,278
Service cost	55	49	$ 59
Interest cost	148	180	167
Actuarial losses	370	535
Settlement		(240)
Benefits paid	(226)	(209)
Projected benefit obligation at end of year	4,940	4,593	4,278
Change in Plan Assets
Plan assets at fair value at beginning of year	4,236	3,748
Actual return on plan assets	760	931
Company contributions	6	6
Settlement		(240)
Benefits paid	(226)	(209)
Plan assets at fair value at end of year	4,776	4,236	3,748
Unfunded Liability	(164)	(357)
Amounts Recognized in Balance Sheet
Postretirement Benefits	(199)	(357)
Other Assets	35
Total of post retirement benefits	(164)	(357)
Amounts Recognized in Accumulated Other Comprehensive Loss
Actuarial losses	423	622
Prior service cost	1	9
Total amount recognized in accumulated other comprehensive income	424	631
Accumulated benefit obligation	4,739	4,345
International
Change in Projected Benefit Obligations
Projected benefit obligation at beginning of year	9,647	8,111
Service cost	140	112	138
Interest cost	301	333	304
Contribution by plan participants	94	63
Actuarial losses	1,233	1,304
Currency effect	68	50
Settlement	(5)	(17)
Benefits paid	(338)	(309)
Projected benefit obligation at end of year	11,140	9,647	8,111
Change in Plan Assets
Plan assets at fair value at beginning of year	9,363	7,872
Actual return on plan assets	1,282	1,676
Currency effect	72	59
Company contributions	20	19
Contributions by plan participants	94	63
Settlement		(17)
Benefits paid	(338)	(309)
Plan assets at fair value at end of year	10,493	9,363	$ 7,872
Unfunded Liability	(647)	(284)
Amounts Recognized in Balance Sheet
Postretirement Benefits	(849)	(602)
Other Assets	202	318
Total of post retirement benefits	(647)	(284)
Amounts Recognized in Accumulated Other Comprehensive Loss
Actuarial losses	1,981	1,638
Total amount recognized in accumulated other comprehensive income	1,981	1,638
Accumulated benefit obligation	$ 10,844	$ 9,376