ASC 606 Adoption And Revenue Recognition (Changes In Contract Assets And Contract Liabilities) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Jan. 01, 2018
ASC 606 Adoption And Revenue Recognition [Abstract]
Contract assets, Beginning balance	$ 77
Revenue recognized included in opening contract balance	(38)
Credits granted, excluding amounts recognized as revenue	36
Contract assets, Ending balance	75
Contract liabilities, Beginning balance	(60)
Revenue recognized included in opening contract balance	90
Cash received, excluding amounts recognized as revenue	(109)
Other	6
Contract liabilities, Ending balance	(73)
Short-term contract assets	38	$ 40
Long-term contract assets	37	37
Short-term contract liabilities	45	41
Long-term contract liabilities	$ 28	$ 19

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