Comprehensive Income (Schedule Of Reclassifications Out Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of services rendered and products sold	$ 400	$ 368	$ 1,104	$ 1,036
Interest expense	39	41	115	128
Interest and net investment income	(1)		(5)	(8)
Provision for income taxes	46	32	76	91
Total reclassifications for the period	(70)	(49)	(124)	(144)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	(2)	(2)	(3)	(1)
Unrealized Losses on Derivatives [Member] | Amount Reclassified from Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net losses on derivatives	(2)	(3)	(8)	(8)
Provision for income taxes	1	1	3	3
Total reclassifications for the period	(2)	(2)	(5)	(5)
Unrealized Losses on Derivatives [Member] | Amount Reclassified from Accumulated Other Comprehensive Income (Loss) [Member] | Fuel Swap Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of services rendered and products sold	(1)	(1)	(3)	(4)
Unrealized Losses on Derivatives [Member] | Amount Reclassified from Accumulated Other Comprehensive Income (Loss) [Member] | Interest Rate Swap Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (2)	(2)	(5)	(4)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Amount Reclassified from Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and net investment income			3	6
Provision for income taxes			(1)	(2)
Total reclassifications for the period			$ 2	$ 4