Postretirement Benefits (Narrative) (Details) - Other Postretirement Benefits Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increased in the accumulated postretirement benefit obligation due to a 1% increase in annual health care cost trend rate	$ 6
Decreased in the accumulated postretirement benefit obligation due to a 1% decrease in the annual trend rat	4
Defined benefit plan, effect of one percentage point increase on service and interest cost components	1
Total recognized in other comprehensive income	2
Total recognized in net periodic benefit cost or OCI	3	$ (25)	$ 0
Expected amortization of gain (loss), next fiscal year	2
Expected amortization of prior service cost (credit), next fiscal year	(4)
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increased in the accumulated postretirement benefit obligation due to a 1% increase in annual health care cost trend rate	12
Decreased in the accumulated postretirement benefit obligation due to a 1% decrease in the annual trend rat	10
Defined benefit plan, effect of one percentage point increase on service and interest cost components	1
Total recognized in other comprehensive income	8
Total recognized in net periodic benefit cost or OCI	25	$ 42	$ 17
Expected amortization of gain (loss), next fiscal year	8
Expected amortization of prior service cost (credit), next fiscal year	$ (2)