Revenue Recognition (Changes In Contract Assets And Contract Liabilities) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Revenue Recognition [Abstract]
Contract current assets, Beginning balance	$ 37	$ 44
Contract current assets, Revenue recognized included in opening contract balance	(18)	(18)
Contract current assets, Credits granted, excluding amounts recognized as revenue	1	17
Contract current assets, Reclassified between current and noncurrent		4
Contract current assets, Reclassified to held for sale		(3)
Contract current assets, Ending balance	20	44
Contract noncurrent assets, Beginning balance	8	25
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		(4)
Contract noncurrent assets, Reclassified to held for sale		(1)
Contract current assets, Ending balance	8	16
Contract current liabilities, Beginning balance	41	49
Contract current liabilities, Revenue recognized included in opening contract balance	(33)	(38)
Contract current liabilities, Cash received, excluding amounts recognized as revenue	42	34
Contract current liabilities, Reclassified between current and noncurrent, NonCurrent	1	(1)
Contract current liabilities, Reclassified to held for sale		(3)
Contract current liabilities, Ending balance	51	41
Contract noncurrent liabilities, Beginning balance	21	22
Contract noncurrent liabilities, Revenue recognized included in opening contract balance	(7)	(11)
Contract noncurrent liabilities, Cash received, excluding amounts recognized as revenue	7	7
Contract current liabilities, Reclassified between current and noncurrent	(1)	1
Contract noncurrent liabilities, Reclassified to held for sale		(1)
Contract noncurrent liabilities, Ending balance	$ 20	$ 18