Acquisitions (Acqusition And Integration Costs) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Acquisition costs									$ 23	$ 45	$ 15
Integration costs									413	191	127
Acquisition and integration costs	$ 49	$ 122	$ 127	$ 138	$ 86	$ 58	$ 35	$ 57	436	236	142
Verizon Transaction
Business Acquisition [Line Items]
Acquisition costs									23	44
Integration costs									412	152
Connecticut Transaction
Business Acquisition [Line Items]
Acquisition costs										1	15
Integration costs									$ 1	$ 39	$ 127