Acquisitions (Narrative) (Details) item in Millions, customer in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($) customer item	Jun. 30, 2016 USD ($) customer item	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Cash paid for acquisition		$ 9,886,000,000
Capital Expenditures Integration Activities		88,000,000	$ 38,000,000
Connecticut Operations [Member]
Business Acquisition [Line Items]
Acquisition purchase price					$ 2,018,000,000
Capital Expenditures Integration Activities			19,000,000
Verizon Transaction [Member]
Business Acquisition [Line Items]
Acquisition purchase price	$ 10,540,000,000	$ 10,540,000,000
Number of voice connections acquired | customer	2.6	2.6
Number of broadband connections acquired | item	2.2	2.2
Number of video connections acquired | item	1.2	1.2
Revenue	$ 1,282,000,000	$ 1,282,000,000
Operating income	264,000,000	264,000,000
Proceeds from equity issuance				$ 2,750,000,000
Capital Expenditures Integration Activities		88,000,000	$ 19,000,000
Senior And Subsidiary Unsecured Debt [Member] | Verizon Transaction [Member]
Business Acquisition [Line Items]
Debt Instrument, Face Amount	$ 6,600,000,000	$ 6,600,000,000		$ 6,600,000,000