Acquisitions and Divestitures (Schedule of Balance Sheet Items Classified as Held for Sale) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Acquisitions and Divestitures [Abstract]
Other current assets	$ 4	$ 21
Other assets, net	$ 14	154
Accrued liabilities		$ 44

Amount classified as accrued liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.

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Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant