Valuation And Qualifying Accounts And Reserves (Schedule Of Valuation And Qualifying Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Balance at Beginning of Year	$ 72	$ 70	$ 81
Additions	3	16	24
Deductions	(6)	(16)	(32)
Other	4	2	(3)
Balance at End of Year	$ 73	$ 72	$ 70