Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Components of net periodic benefit cost:
(Gain) loss on remeasurement of pension obligations		$ 122	$ 0	$ (132)
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans	$ 54		160
Expected full year contributions to pension and other postretirement benefit plans during the year	310		310
Other Postretirement Benefits Plan
Components of net periodic benefit cost:
Service cost	25	24	50	47
Interest cost	16	27	32	53
Expected return on plan assets	(1)	(3)	(3)	(6)
Amortization of prior service cost / (credit)	(10)	(10)	(20)	(19)
Curtailments, settlements and termination benefits	0	0	0	0
(Gain) loss on remeasurement of pension obligations	0	0	0	0
Net periodic benefit cost (benefit)	30	38	59	75
UNITED STATES
Components of net periodic benefit cost:
Service cost	0	0	0	0
Interest cost	83	121	165	242
Expected return on plan assets	(179)	(198)	(358)	(396)
Amortization of prior service cost / (credit)	0	0	0	0
Curtailments, settlements and termination benefits	0	0	0	0
(Gain) loss on remeasurement of pension obligations	0	2	0	2
Net periodic benefit cost (benefit)	(96)	(75)	(193)	(152)
Foreign Plan
Components of net periodic benefit cost:
Service cost	15	14	29	28
Interest cost	13	21	27	40
Expected return on plan assets	(33)	(38)	(65)	(73)
Amortization of prior service cost / (credit)	0	0	0	0
Curtailments, settlements and termination benefits	0	21	0	21
(Gain) loss on remeasurement of pension obligations	0	120	0	(134)
Net periodic benefit cost (benefit)	$ (5)	$ 138	$ (9)	$ (118)