Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share
Net income attributable to Parent	$ 2,237	$ 1,996	$ 6,399	$ 6,192
Basic shares attributable to Comcast Corporation shareholders	2,403	2,472	2,419	2,498
Assumed exercise or issuance of shares relating to stock plans	28	30	27	32
Diluted shares attributable to Comcast Corporation shareholders	2,431	2,502	2,446	2,530
Basic earnings per common share attributable to Comcast Corporation shareholders	$ 0.93	$ 0.81	$ 2.65	$ 2.48
Diluted earnings per common share attributable to Comcast Corporation shareholders	$ 0.92	$ 0.8	$ 2.62	$ 2.45