Comprehensive (Loss) Income (Schedule Of Reclassifications Out Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Impact of income taxes	$ (18)		$ (14)		$ (16)	$ (17)
Net Income	53	$ 14	59	$ 70	67	129
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on derivatives:	(2)		2		(2)	3
Impact of income taxes	1				1
Net Income	(2)		2		(1)	2
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Fuel Swap Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on derivatives:	(2)				$ (2)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Cross Currency Swap And Net Investment Hedge [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (losses) on derivatives:	$ (1)		$ 2			$ 3