Summary of Significant Accounting Policies (Revenue By Product Line) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Product Information
Revenues	$ 2,360	$ 2,287	$ 2,259	$ 2,202	$ 2,148	$ 2,118	$ 1,972	$ 1,917	$ 9,108	$ 8,155	$ 7,504
Video [Member]
Product Information
Revenues									4,443	4,040	3,649
Internet [Member]
Product Information
Revenues									2,576	2,186	1,866
Voice [Member]
Product Information
Revenues									575	644	828
Commercial [Member]
Product Information
Revenues									993	812	648
Advertising sales [Member]
Product Information
Revenues									341	291	334
Other [Member]
Product Information
Revenues									$ 180	$ 182	$ 179