Postretirement Benefits (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits
Pension contributions
Contributions to pension plans	$ 33	$ 36	$ 96	$ 113
Expected full year contributions to pension plans during the year	150		150
U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost	29	45	59	91
Interest cost	130	152	259	303
Expected return on plan assets	(189)	(224)	(378)	(448)
Amortization of prior service cost / (credit)	0	0	0	0
Net actuarial loss / (gain)	0	(8)	0	(8)
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	(30)	(35)	(60)	(62)
Curtailments, settlements and termination benefits	0	(19)	0	(19)
Total cost (benefit) included in operating profit	(30)	(54)	$ (60)	$ (81)
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	28	$ 46	$ 57
Interest cost	30	36	60	75
Expected return on plan assets	(59)	(68)	(117)	(137)
Amortization of prior service cost / (credit)	0	0	0	0
Net actuarial loss / (gain)	0	0	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	(6)	(4)	(11)	(5)
Curtailments, settlements and termination benefits	0	0	0	0
Total cost (benefit) included in operating profit	(6)	(4)	$ (11)	$ (5)
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	21	25	$ 41	$ 50
Interest cost	32	46	65	92
Expected return on plan assets	(11)	(14)	(22)	(28)
Amortization of prior service cost / (credit)	(15)	(14)	(30)	(27)
Net actuarial loss / (gain)	0	0	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits	27	43	54	87
Curtailments, settlements and termination benefits	0	0	(2)	0
Total cost (benefit) included in operating profit	27	$ 43	$ 52	$ 87
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		$ 90
Change in Accounting Estimate, Effect of Change on Diluted Earnings Per Share	$ 0.05		$ 0.10
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%