Defined Benefit Postretirement Plans Defined Benefit Postretirement Plan - Obligations and Funded Status (Details) - Foreign Plan [Member] $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 0	$ 511
Benefit obligations, beginning balance	511	599
Interest cost	8	14
Defined Benefit Plan, Accumulated Benefit Obligation, Increase (Decrease) for Plan Amendment	0	3
Defined Benefit Plan, Benefit Obligation, Divestiture	(549)	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	36	(38)
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)	6	(29)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	(23)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(12)	(15)
Benefit obligations, ending balance	0	511
Fair value of plan assets, beginning balance	594	670
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	68	(21)
Defined Benefit Plan, Plan Assets, Contributions by Employer	8	17
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	8	(34)
Defined Benefit Plan, Plan Assets, Divestiture	(666)	0
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	(23)
Defined Benefit Plan, Plan Assets, Benefits Paid	(12)	(15)
Fair value of plan assets, ending balance	0	594
Defined Benefit Plan, Funded (Unfunded) Status of Plan	0	83
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	0	59
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	0	5
Noncurrent assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	0	83
Accrued benefit cost
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	$ 0	$ 83