Acquisitions (Narrative) (Details) item in Millions, $ in Millions		1 Months Ended	3 Months Ended								12 Months Ended
	Apr. 01, 2016 USD ($) item	Oct. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition, Date of Acquisition [Abstract]
Cash paid for acquisition												$ 9,871
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Purchase accounting adjustments											$ 98
Goodwill, net			$ 7,024				$ 9,674				7,024	9,674	$ 7,166
Revenue			2,217	$ 2,251	$ 2,304	$ 2,356	2,409	$ 2,524	$ 2,608	$ 1,355	9,128	8,896	5,576
Operating income			(1,754)	$ 309	$ (394)	$ 271	255	$ 264	$ 311	$ 58	(1,568)	888	745
Capital Expenditures Integration Activities											34	142	153
CTF Transaction [Member]
Business Acquisition, Date of Acquisition [Abstract]
Acquisition purchase price	$ 10,540
Working Capital And Net Debt Settlement Payments Received		$ 15
Number of video connections acquired | item	1.2
Number of broadband connections acquired | item	2.1
Number of voice connections acquired | item	2.5
Cash paid for acquisition	$ 9,871
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Other intangibles adjustment											100
Other intangibles acquired			2,262				$ 2,162				2,262	2,162
Measurement period adjustments											20
Property and equipment adjustment											(140)
Current liabilities adjustment											61
Purchase accounting adjustments											98
Goodwill, net			$ 2,606								2,606
Revenue												3,622
Operating income												582
Capital Expenditures Integration Activities											$ 34	$ 142	129
Connecticut Transaction [Member]
Business Acquisition, Date of Acquisition [Abstract]
Cash paid for acquisition														$ 2,018
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Capital Expenditures Integration Activities													$ 24