Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans	$ 47		$ 217
Expected full year contributions to pension and other postretirement benefit plans during the year	250		250
Other Postretirement Benefits Plan
Components of net periodic benefit cost:
Service cost	24	$ 19	71	$ 60
Interest cost	26	34	79	102
Expected return on plan assets	(4)	(4)	(10)	(14)
Amortization of prior service cost / (credit)	(9)	(10)	(28)	(30)
(Gain) loss on remeasurement of pension obligations	0	0	0	0
Curtailments, settlements and termination benefits	0	0	0	0
Net periodic benefit cost (benefit)	37	39	112	118
UNITED STATES
Components of net periodic benefit cost:
Service cost	0	29	0	86
Interest cost	120	150	362	450
Expected return on plan assets	(197)	(180)	(593)	(540)
Amortization of prior service cost / (credit)	0	0	0	0
(Gain) loss on remeasurement of pension obligations	(2)	0	0	0
Curtailments, settlements and termination benefits	0	0	0	0
Net periodic benefit cost (benefit)	(79)	(1)	(231)	(4)
Foreign Plan
Components of net periodic benefit cost:
Service cost	13	20	41	61
Interest cost	17	23	57	70
Expected return on plan assets	(34)	(37)	(107)	(112)
Amortization of prior service cost / (credit)	0	0	0	0
(Gain) loss on remeasurement of pension obligations	79	0	(55)	0
Curtailments, settlements and termination benefits	4	0	25	0
Net periodic benefit cost (benefit)	$ 79	$ 6	$ (39)	$ 19