Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans	$ 119
Expected full year contributions to pension and other postretirement benefit plans during the year	315
UNITED STATES
Components of net periodic benefit cost:
Service cost	29	$ 32
Interest cost	150	133
Expected return on plan assets	(181)	(202)
Amortization of prior service cost / (credit)	0	0
Net periodic benefit cost (benefit)	(2)	(37)
Foreign Plan
Components of net periodic benefit cost:
Service cost	21	22
Interest cost	23	25
Expected return on plan assets	(37)	(56)
Amortization of prior service cost / (credit)	0	0
Net periodic benefit cost (benefit)	7	(9)
Other Postretirement Benefits Plan
Components of net periodic benefit cost:
Service cost	20	21
Interest cost	34	31
Expected return on plan assets	(5)	(8)
Amortization of prior service cost / (credit)	(10)	(9)
Net periodic benefit cost (benefit)	$ 39	$ 35