Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans	$ 106	$ 115
Expected full year contributions to pension and other postretirement benefit plans during the year	610
U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost	29	30
Interest cost	131	129
Expected return on plan assets	(184)	(189)
Amortization of prior service cost / (credit)	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	(24)	(30)
Curtailments, settlements and termination benefits	9	0
Total cost (benefit) included in operating profit	$ (15)	$ (30)
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost	4.20%	4.50%
Discount rate used to measure interest cost	3.30%	3.40%
Expected return on plan assets (as a percent)	6.70%	6.90%
Rate of compensation increase (as a percent)	4.00%	4.00%
Non-U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 23	$ 23
Interest cost	25	30
Expected return on plan assets	(57)	(58)
Amortization of prior service cost / (credit)	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	(9)	(5)
Curtailments, settlements and termination benefits	20	0
Total cost (benefit) included in operating profit	$ 11	$ (5)
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost	2.30%	2.90%
Discount rate used to measure interest cost	2.30%	2.80%
Expected return on plan assets (as a percent)	5.90%	6.10%
Rate of compensation increase (as a percent)	4.00%	3.50%
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	$ 19	$ 20
Interest cost	33	33
Expected return on plan assets	(9)	(11)
Amortization of prior service cost / (credit)	(5)	(15)
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	38	27
Curtailments, settlements and termination benefits	0	(2)
Total cost (benefit) included in operating profit	$ 38	$ 25
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost	3.90%	4.40%
Discount rate used to measure interest cost	3.30%	3.30%
Expected return on plan assets (as a percent)	7.50%	7.50%
Rate of compensation increase (as a percent)	4.00%	4.00%