Comprehensive Income (Schedule Of Reclassifications Out Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of services rendered and products sold	$ 379	$ 365	$ 704	$ 668
Interest expense	38	42	76	88
Interest and net investment income	(4)	(7)	(4)	(7)
Provision for income taxes	7	42	30	59
Total reclassifications for the period	(16)	(67)	(54)	(94)
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)	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)	(5)	(5)
Provision for income taxes	1	1	2	2
Total reclassifications for the period	(1)	(2)	(3)	(3)
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)	(2)	(3)
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)	(3)	(2)
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	3	6
Provision for income taxes	(1)	(2)	(1)	(2)
Total reclassifications for the period	$ 2	$ 4	$ 2	$ 4