Pension and Other Postretirement Benefit Plans (Change in Benefit Obligation) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2017	Jun. 30, 2011	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year			$ 394	$ 376
Service cost			7	7	$ 7
Interest cost			15	16	18
Plan participants' contributions			0	0
Actuarial loss (gain)			(16)	15
Benefits paid			(36)	(40)
Plan amendments		$ (138)	4	16
Transfer of liabilities			0	0
Special termination benefit			0	4
Settlements / curtailment (gain)			0	0
Foreign currency exchange rates			(5)	0
Reclassification of obligation to held for sale			(7)	0
Benefit obligation, end of year	$ 394		356	394	376
United States Pension Benefits \| Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year			3,415	3,415
Service cost			2	2	3
Interest cost			118	134	147
Plan participants' contributions			0	0
Actuarial loss (gain)			(197)	188
Benefits paid			(305)	(260)
Plan amendments			0	0
Transfer of liabilities	64		0	(64)
Special termination benefit			0	0
Settlements / curtailment (gain)			0	0
Foreign currency exchange rates			0	0
Reclassification of obligation to held for sale			0	0
Benefit obligation, end of year	3,415		3,033	3,415	3,415
Accumulated benefit obligation, end of year	3,403		3,022	3,403
Foreign Pension Benefits \| Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning of year			952	855
Service cost			5	5	5
Interest cost			23	23	27
Plan participants' contributions			1	1
Actuarial loss (gain)			(33)	30
Benefits paid			(31)	(32)
Plan amendments			1	0
Transfer of liabilities			0	0
Special termination benefit			(5)	0
Settlements / curtailment (gain)			(22)	(12)
Foreign currency exchange rates			(53)	82
Reclassification of obligation to held for sale			(4)	0
Benefit obligation, end of year	952		834	952	$ 855
Accumulated benefit obligation, end of year	$ 914		$ 804	$ 914

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of increase (decrease) in plan assets of defined benefit plan from assets transferred into (from) plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of decrease in benefit obligation of defined benefit plan from disposal or classification as held-for-sale.

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Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from settlement and curtailment.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of increase in benefit obligation for benefits provided to employees payable from defined benefit plan or payable upon retirement.

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