Goodwill And Other Intangibles (Schedule Of Goodwill Activity) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 7,166	$ 7,205
Goodwill, Ending Balance	9,674	7,166
Connecticut Transaction
Goodwill [Line Items]
Goodwill, Beginning Balance	815
Goodwill, Purchase Accounting Adjustments		(53)
Goodwill, Ending Balance		815
Other Acquisitions [Member]
Goodwill [Line Items]
Goodwill, Acquired During the Period		$ 14
Verizon Transaction
Goodwill [Line Items]
Goodwill, Acquired During the Period	2,508
Goodwill, Ending Balance	$ 2,508