Pension, Other Postretirement Benefits and Savings Plans - Changes in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation:
Curtailments/settlements/termination benefits	$ 22	$ 19	$ 17
Other Postretirement Benefits
Change in benefit obligation:
Beginning balance	(286)	(294)
Service cost — benefits earned	(3)	(4)	(3)
Interest cost	(12)	(13)	(12)
Plan amendments	14	(3)
Actuarial gain (loss)	19	15
Participant contributions	(13)	(14)
Curtailments/settlements/termination benefits	0	0
Foreign currency translation	15	(9)
Benefit payments	32	36
Ending balance	(234)	(286)	(294)
Change in plan assets:
Beginning balance	4	4
Actual return on plan assets	0	0
Company contributions to plan assets	2	2
Cash funding of direct participant payments	16	20
Participant contributions	13	14
Settlements	0	0
Foreign currency translation	0	0
Benefit payments	(32)	(36)
Ending balance	3	4	4
Funded status at end of year	(231)	(282)
United States
Change in plan assets:
Beginning balance	4,978
Ending balance	4,445	4,978
United States | Pension Plan
Change in benefit obligation:
Beginning balance	(5,331)	(5,285)
Service cost — benefits earned	(4)	(4)	(5)
Interest cost	(157)	(160)	(164)
Plan amendments	0	0
Actuarial gain (loss)	315	(303)
Participant contributions	0	0
Curtailments/settlements/termination benefits	25	55
Foreign currency translation	0	0
Benefit payments	418	366
Ending balance	(4,734)	(5,331)	(5,285)
Change in plan assets:
Beginning balance	4,978	4,972
Actual return on plan assets	(110)	417
Company contributions to plan assets	0	0
Cash funding of direct participant payments	17	10
Participant contributions	0	0
Settlements	(22)	(55)
Foreign currency translation	0	0
Benefit payments	(418)	(366)
Ending balance	4,445	4,978	4,972
Funded status at end of year	(289)	(353)
United States | Other Postretirement Benefits
Change in plan assets:
Funded status at end of year	(112)	(132)
Non-U.S.
Change in plan assets:
Beginning balance	2,806
Ending balance	2,464	2,806
Non-U.S. | Pension Plan
Change in benefit obligation:
Beginning balance	(3,109)	(2,863)
Service cost — benefits earned	(28)	(31)	(29)
Interest cost	(69)	(71)	(80)
Plan amendments	(29)	(3)
Actuarial gain (loss)	40	(29)
Participant contributions	(2)	(2)
Curtailments/settlements/termination benefits	113	21
Foreign currency translation	177	(280)
Benefit payments	133	149
Ending balance	(2,774)	(3,109)	(2,863)
Change in plan assets:
Beginning balance	2,806	2,507
Actual return on plan assets	4	146
Company contributions to plan assets	36	56
Cash funding of direct participant payments	21	24
Participant contributions	2	2
Settlements	(112)	(11)
Foreign currency translation	(160)	231
Benefit payments	(133)	(149)
Ending balance	2,464	2,806	$ 2,507
Funded status at end of year	(310)	(303)
Non-U.S. | Other Postretirement Benefits
Change in plan assets:
Funded status at end of year	$ (119)	$ (150)