Defined Benefit Postretirement Plans and Defined Contribution Plan - Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
UNITED STATES
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	$ 320	$ 378
Change in benefit obligations:
Benefit obligations at January 1	384	397
Service cost	18	22
Interest cost	12	13
Plan amendment	0	0
Actuarial loss	(20)	42
Foreign currency exchange rate changes	0	0
Settlements paid	(62)	(84)
Benefits paid	(6)	(6)
Benefit obligations at December 31	326	384
Change in fair value of plan assets:
Fair value of plan assets at January 1	216	227
Actual return on plan assets	(6)	27
Employer contributions	61	52
Foreign currency exchange rate changes	0	0
Settlements paid	(62)	(84)
Benefits paid	(6)	(6)
Fair value of plan assets at December 31	203	216
Funded status of plans at December 31
Funded status of plans at December 31	(123)	(168)
Amounts recognized in the consolidated balance sheets:
Noncurrent assets	0	0
Current liabilities	(5)	(6)
Noncurrent liabilities	(118)	(162)
Accrued benefit cost	(123)	(168)
Pretax amounts in accumulated other comprehensive loss:
Net loss (gain)	90	122
Prior service cost (credit)	(36)	(45)
Foreign Plan [Member]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	511	599
Change in benefit obligations:
Benefit obligations at January 1	599	583
Service cost	0	0
Interest cost	14	17
Plan amendment	3	0
Actuarial loss	(38)	(7)
Foreign currency exchange rate changes	(29)	52
Settlements paid	(23)	(31)
Benefits paid	(15)	(15)
Benefit obligations at December 31	511	599
Change in fair value of plan assets:
Fair value of plan assets at January 1	670	595
Actual return on plan assets	(21)	47
Employer contributions	17	17
Foreign currency exchange rate changes	(34)	57
Settlements paid	(23)	(31)
Benefits paid	(15)	(15)
Fair value of plan assets at December 31	594	670
Funded status of plans at December 31
Funded status of plans at December 31	83	71
Amounts recognized in the consolidated balance sheets:
Noncurrent assets	83	71
Current liabilities	0	0
Noncurrent liabilities	0	0
Accrued benefit cost	83	71
Pretax amounts in accumulated other comprehensive loss:
Net loss (gain)	59	58
Prior service cost (credit)	5	3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	96	221
Change in benefit obligations:
Benefit obligations at January 1	221	227
Service cost	2	2
Interest cost	7	8
Plan amendment	(99)	0
Actuarial loss	(15)	5
Foreign currency exchange rate changes	0	0
Settlements paid	0	0
Benefits paid	(20)	(21)
Benefit obligations at December 31	96	221
Change in fair value of plan assets:
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Employer contributions	20	21
Foreign currency exchange rate changes	0	0
Settlements paid	0	0
Benefits paid	(20)	(21)
Fair value of plan assets at December 31	0	0
Funded status of plans at December 31
Funded status of plans at December 31	(96)	(221)
Amounts recognized in the consolidated balance sheets:
Noncurrent assets	0	0
Current liabilities	(19)	(21)
Noncurrent liabilities	(77)	(200)
Accrued benefit cost	(96)	(221)
Pretax amounts in accumulated other comprehensive loss:
Net loss (gain)	14	30
Prior service cost (credit)	$ (147)	$ (56)