Revenue Recognition (Changes In Contract Assets And Contract Liabilities) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Revenue Recognition [Abstract]
Contract current assets, Beginning balance	$ 44	$ 40
Contract current assets, Revenue recognized included in opening contract balance	(18)	(21)
Contract current assets, Credits granted, excluding amounts recognized as revenue	17	27
Contract current assets, Other	4	(4)
Contract current assets, Reclassified to Held for Sale	(3)
Contract current assets, Ending balance	44	42
Contract noncurrent assets, Beginning balance	25	37
Contract noncurrent assets, Revenue recognized included in opening contract balance	(5)
Contract noncurrent assets, Credits granted, excluding amounts recognized as revenue	1
Contract noncurrent assets, Other	(4)	4
Contract noncurrent assets, Reclassified to held for sale	(1)
Contract current assets, Ending balance	16	41
Contract current liabilities, Beginning balance	49	41
Contract current liabilities, Revenue recognized included in opening contract balance	(38)	(64)
Contract current liabilities, Cash received, excluding amounts recognized as revenue	34	86
Contract current liabilities, Other	(1)	(12)
Contract current liabilities, Reclassified to Held for Sale	(3)
Contract current liabilities, Ending balance	41	51
Contract noncurrent liabilities, Beginning balance	22	19
Contract noncurrent liabilities, Revenue recognized included in opening contract balance	(11)
Contract noncurrent liabilities, Cash received, excluding amounts recognized as revenue	7
Contract noncurrent liabilities, Other	1	6
Contract noncurrent liabilities, Reclassified to Held for Sale	(1)
Contract noncurrent liabilities, Ending balance	$ 18	$ 25