Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Components of net periodic benefit cost:
(Gain) loss on remeasurement of pension obligations		$ 77	$ 0	$ (55)
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans	$ 69		229
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	75	71
Interest cost	16	26	48	79
Expected return on plan assets	(1)	(4)	(4)	(10)
Amortization of prior service cost / (credit)	(11)	(9)	(31)	(28)
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)	29	37	88	112
UNITED STATES
Components of net periodic benefit cost:
Service cost	0	0	0	0
Interest cost	82	120	247	362
Expected return on plan assets	(180)	(197)	(538)	(593)
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	0
Net periodic benefit cost (benefit)	(98)	(79)	(291)	(231)
Foreign Plan
Components of net periodic benefit cost:
Service cost	15	13	44	41
Interest cost	16	17	43	57
Expected return on plan assets	(33)	(34)	(98)	(107)
Amortization of prior service cost / (credit)	0	0	0	0
Curtailments, settlements and termination benefits	0	4	0	25
(Gain) loss on remeasurement of pension obligations	0	79	0	(55)
Net periodic benefit cost (benefit)	$ (2)	$ 79	$ (11)	$ (39)