Retirement Benefits (Net Amount Included In Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 134	$ 202
Current liabilities	(6)	(5)
Noncurrent liabilities	(53)	(57)
Net amount at December 31	75	140
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0	0
Current liabilities	0	0
Noncurrent liabilities	(95)	(168)
Net amount at December 31	$ (95)	$ (168)