Revenue Recognition (Changes In Contract Assets And Contract Liabilities) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Revenue Recognition [Abstract]
Contract current assets, Beginning balance	$ 44	$ 40
Contract current assets, Revenue recognized included in opening contract balance	(29)	(38)
Contract current assets, Credits granted, excluding amounts recognized as revenue	23	36
Contract current assets, Reclassified between Current and NonCurrent	5
Contract current assets, Reclassified to held for sale	(3)
Contract current assets, Ending balance	40	38
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 current assets, Reclassified between Current and NonCurrent	(5)
Contract noncurrent assets, Reclassified to held for sale	(1)
Contract current assets, Ending balance	15	37
Contract current liabilities, Beginning balance	49	41
Contract current liabilities, Revenue recognized included in opening contract balance	(56)	(86)
Contract current liabilities, Cash received, excluding amounts recognized as revenue	58	106
Contract current liabilities, Reclassified between Current and NonCurrent, NonCurrent	(2)	(10)
Contract current liabilities, Other		(6)
Contract current liabilities, Reclassified to held for sale	(5)
Contract current liabilities, Ending balance	44	45
Contract noncurrent liabilities, Beginning balance	22	19
Contract noncurrent liabilities, Revenue recognized included in opening contract balance	(14)	(4)
Contract noncurrent liabilities, Cash received, excluding amounts recognized as revenue	9	3
Contract current liabilities, Reclassified between Current and NonCurrent	2	10
Contract noncurrent liabilities, Reclassified to held for sale	(1)
Contract noncurrent liabilities, Ending balance	$ 18	$ 28