Postretirement Benefits (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits
Pension contributions
Contributions to pension plans	$ 63	$ 77
Expected full year contributions to pension plans during the year	150
U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost	30	46
Interest cost	129	151
Expected return on plan assets	(189)	(224)
Amortization of:
Prior service cost / (credit)	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	(30)	(27)
Curtailments, settlements and termination benefits	0	0
Total cost (benefit) included in operating profit	$ (30)	$ (27)
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost	4.50%	3.80%
Discount rate used to measure interest cost	3.40%	3.80%
Expected return on plan assets (as a percent)	6.90%	7.40%
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	$ 29
Interest cost	30	39
Expected return on plan assets	(58)	(69)
Amortization of:
Prior service cost / (credit)	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	(5)	(1)
Curtailments, settlements and termination benefits	0	0
Total cost (benefit) included in operating profit	$ (5)	$ (1)
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost	2.90%	3.30%
Discount rate used to measure interest cost	2.80%	3.30%
Expected return on plan assets (as a percent)	6.10%	6.80%
Rate of compensation increase (as a percent)	3.50%	4.00%
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	$ 20	$ 25
Interest cost	33	46
Expected return on plan assets	(11)	(14)
Amortization of:
Prior service cost / (credit)	(15)	(13)
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	27	44
Curtailments, settlements and termination benefits	(2)	0
Total cost (benefit) included in operating profit	$ 25	$ 44
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost	4.40%	3.90%
Discount rate used to measure interest cost	3.30%	3.90%
Expected return on plan assets (as a percent)	7.50%	7.80%
Rate of compensation increase (as a percent)	4.00%	4.00%
Restatement Adjustment
Defined Benefit Plan Disclosure
Pension and other postretirement benefits (OPEB) expense	$ 45
Change in Accounting Estimate, Effect of Change on Diluted Earnings Per Share	$ 0.06
Previous Accounting Method | U.S. Pension Benefits
Defined Benefit Plan Disclosure
Discount rate (as a percent)	4.20%
Previous Accounting Method | Non-U.S. Pension Benefits
Defined Benefit Plan Disclosure
Discount rate (as a percent)	3.20%
Previous Accounting Method | Other Postretirement Benefits
Defined Benefit Plan Disclosure
Discount rate (as a percent)	4.10%