Retirement Benefits (Net Amount Included In Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 248	$ 212
Current liabilities	(6)	(6)
Noncurrent liabilities	(65)	(60)
Net amount at December 31	177	146
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0	0
Current liabilities	0	0
Noncurrent liabilities	(8)	(56)
Net amount at December 31	$ (8)	$ (56)