Accounts Receivable (Schedule Of Allowance For Doubtful Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for Doubtful Accounts, Beginning of Period	$ 57
Allowance for Doubtful Accounts, End of Period	131	$ 57
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for Doubtful Accounts, Beginning of Period	57	72	$ 71
Charged to Other Revenue	164	67	61
Charged (Credited) to Switched and Nonswitched Revenue and Other Accounts	15	(17)
Write-offs, net of Recoveries	(105)	(65)	(60)
Allowance for Doubtful Accounts, End of Period	$ 131	$ 57	$ 72