Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 12	$ 26	$ 24
Interest cost	14	18	29	35
Expected return on plan assets	(19)	(18)	(37)	(36)
Amortization of unrecognized prior service credit	(22)	(21)	(45)	(43)
Curtailments	0	(1)	(1)	(1)
Net periodic benefit cost	(14)	(10)	(28)	(21)
U.S. | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	88	74	175	144
Interest cost	109	113	217	228
Expected return on plan assets	(195)	(205)	(388)	(411)
Amortization of unrecognized prior service credit	(12)	(12)	(25)	(25)
Net loss amortization	76	35	152	70
Termination benefits	1	3	4	5
Curtailments	0	0	2	1
Settlements	9	0	9	0
Net periodic benefit cost	76	8	146	12
International | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	74	60	148	120
Interest cost	33	44	68	89
Expected return on plan assets	(101)	(107)	(205)	(214)
Amortization of unrecognized prior service credit	(3)	(3)	(6)	(6)
Net loss amortization	31	16	62	31
Termination benefits	0	1	1	1
Curtailments	0	0	(1)	0
Settlements	2	0	2	0
Net periodic benefit cost	$ 36	$ 11	$ 69	$ 21