Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 12	$ 39	$ 36
Interest cost	14	17	43	52
Expected return on plan assets	(19)	(18)	(56)	(54)
Amortization of unrecognized prior service credit	(18)	(20)	(54)	(59)
Net loss amortization	(5)	(3)	(13)	(7)
Termination benefits	0	1	0	1
Curtailments	0	(3)	(1)	(4)
Net periodic benefit cost	(15)	(14)	(42)	(35)
U.S. | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	96	76	270	221
Interest cost	107	115	323	343
Expected return on plan assets	(193)	(202)	(581)	(613)
Amortization of unrecognized prior service credit	(12)	(12)	(37)	(37)
Net loss amortization	75	43	228	113
Termination benefits	1	3	5	7
Curtailments	1	5	4	6
Settlements	2	0	11	0
Net periodic benefit cost	77	28	223	40
International | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	77	58	225	178
Interest cost	35	44	103	133
Expected return on plan assets	(104)	(106)	(310)	(320)
Amortization of unrecognized prior service credit	(3)	(3)	(9)	(9)
Net loss amortization	32	16	94	47
Termination benefits	1	0	2	1
Curtailments	0	0	(1)	0
Settlements	0	0	2	0
Net periodic benefit cost	$ 38	$ 9	$ 106	$ 30