Pension, Other Postretirement Benefits and Savings Plans - Changes in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation:
Curtailments/settlements/termination benefits	$ 19	$ 17	$ 139
Other Postretirement Benefits
Change in benefit obligation:
Beginning balance	(294)	(291)
Newly adopted plans	0	0
Service cost — benefits earned	(4)	(3)	(3)
Interest cost	(13)	(12)	(15)
Plan amendments	(3)	0
Actuarial gain (loss)	15	0
Participant contributions	(14)	(13)
Curtailments/settlements/termination benefits	0	(2)
Foreign currency translation	(9)	(10)
Benefit payments	36	37
Ending balance	(286)	(294)	(291)
Change in plan assets:
Beginning balance	4	3
Newly adopted plans	0	0
Actual return on plan assets	0	1
Company contributions to plan assets	2	2
Cash funding of direct participant payments	20	22
Participant contributions	14	13
Settlements	0	0
Foreign currency translation	0	0
Benefit payments	(36)	(37)
Ending balance	4	4	3
Funded status at end of year	(282)	(290)
United States
Change in plan assets:
Beginning balance	4,972
Ending balance	4,978	4,972
United States | Pension Plan
Change in benefit obligation:
Beginning balance	(5,285)	(5,338)
Newly adopted plans	0	0
Service cost — benefits earned	(4)	(5)	(4)
Interest cost	(160)	(164)	(238)
Plan amendments	0	0
Actuarial gain (loss)	(303)	(171)
Participant contributions	0	0
Curtailments/settlements/termination benefits	55	1
Foreign currency translation	0	0
Benefit payments	366	392
Ending balance	(5,331)	(5,285)	(5,338)
Change in plan assets:
Beginning balance	4,972	5,011
Newly adopted plans	0	0
Actual return on plan assets	417	345
Company contributions to plan assets	0	0
Cash funding of direct participant payments	10	9
Participant contributions	0	0
Settlements	(55)	(1)
Foreign currency translation	0	0
Benefit payments	(366)	(392)
Ending balance	4,978	4,972	5,011
Funded status at end of year	(353)	(313)
United States | Other Postretirement Benefits
Change in plan assets:
Funded status at end of year	(132)	(143)
Non-U.S.
Change in plan assets:
Beginning balance	2,507
Ending balance	2,806	2,507
Non-U.S. | Pension Plan
Change in benefit obligation:
Beginning balance	(2,863)	(2,808)
Newly adopted plans	0	(2)
Service cost — benefits earned	(31)	(29)	(43)
Interest cost	(71)	(80)	(113)
Plan amendments	(3)	0
Actuarial gain (loss)	(29)	(384)
Participant contributions	(2)	(2)
Curtailments/settlements/termination benefits	21	52
Foreign currency translation	(280)	262
Benefit payments	149	128
Ending balance	(3,109)	(2,863)	(2,808)
Change in plan assets:
Beginning balance	2,507	2,493
Newly adopted plans	0	1
Actual return on plan assets	146	393
Company contributions to plan assets	56	56
Cash funding of direct participant payments	24	24
Participant contributions	2	2
Settlements	(11)	(51)
Foreign currency translation	231	(283)
Benefit payments	(149)	(128)
Ending balance	2,806	2,507	$ 2,493
Funded status at end of year	(303)	(356)
Non-U.S. | Other Postretirement Benefits
Change in plan assets:
Funded status at end of year	$ (150)	$ (147)