ASC 606 Adoption And Revenue Recognition (Changes In Contract Assets And Contract Liabilities) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jan. 01, 2018
ASC 606 Adoption And Revenue Recognition [Abstract]
Contract assets, Beginning balance	$ 77
Revenue recognized included in opening balance	(21)
Credits granted, excluding amounts recognized as revenue	27
Contract assets, Ending balance	83
Contract liabilities, Beginning balance	(60)
Revenue recognized included in opening contract balance	64
Cash received, excluding amounts recognized as revenue	(86)
Other	6
Contract liabilities, Ending balance	(76)
Short-term contract assets	42	$ 40
Long-term contract assets	41	37
Short-term contract liabilities	51	41
Long-term contract liabilities	$ 25	$ 19