v2.4.1.9

Quarterly Financial Information (Unaudited) (Details) (USD $) In Millions, except Per Share data, 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
Quarterly Financial Information Disclosure Abstract
Revenue	$ 17,732us-gaap_Revenues	$ 16,791us-gaap_Revenues	$ 16,844us-gaap_Revenues	$ 17,408us-gaap_Revenues	$ 16,926us-gaap_Revenues	$ 16,151us-gaap_Revenues	$ 16,270us-gaap_Revenues	$ 15,310us-gaap_Revenues	$ 68,775us-gaap_Revenues	$ 64,657us-gaap_Revenues	$ 62,570us-gaap_Revenues
Operating income	3,787us-gaap_OperatingIncomeLoss	3,745us-gaap_OperatingIncomeLoss	3,804us-gaap_OperatingIncomeLoss	3,568us-gaap_OperatingIncomeLoss	3,647us-gaap_OperatingIncomeLoss	3,414us-gaap_OperatingIncomeLoss	3,435us-gaap_OperatingIncomeLoss	3,067us-gaap_OperatingIncomeLoss	14,904us-gaap_OperatingIncomeLoss	13,563us-gaap_OperatingIncomeLoss	12,179us-gaap_OperatingIncomeLoss
Net income attributable to Parent	1,925us-gaap_NetIncomeLoss	2,592us-gaap_NetIncomeLoss	1,992us-gaap_NetIncomeLoss	1,871us-gaap_NetIncomeLoss	1,913us-gaap_NetIncomeLoss	1,732us-gaap_NetIncomeLoss	1,734us-gaap_NetIncomeLoss	1,437us-gaap_NetIncomeLoss	8,380us-gaap_NetIncomeLoss	6,816us-gaap_NetIncomeLoss	6,203us-gaap_NetIncomeLoss
Basic earnings per common share attributable to Comcast Corporation shareholders	$ 0.75us-gaap_EarningsPerShareBasic	$ 1us-gaap_EarningsPerShareBasic	$ 0.77us-gaap_EarningsPerShareBasic	$ 0.72us-gaap_EarningsPerShareBasic	$ 0.73us-gaap_EarningsPerShareBasic	$ 0.66us-gaap_EarningsPerShareBasic	$ 0.66us-gaap_EarningsPerShareBasic	$ 0.55us-gaap_EarningsPerShareBasic	$ 3.24us-gaap_EarningsPerShareBasic	$ 2.6us-gaap_EarningsPerShareBasic	$ 2.32us-gaap_EarningsPerShareBasic
Diluted earnings per common share attributable to Comcast Corporation shareholders	$ 0.74us-gaap_EarningsPerShareDiluted	$ 0.99us-gaap_EarningsPerShareDiluted	$ 0.76us-gaap_EarningsPerShareDiluted	$ 0.71us-gaap_EarningsPerShareDiluted	$ 0.72us-gaap_EarningsPerShareDiluted	$ 0.65us-gaap_EarningsPerShareDiluted	$ 0.65us-gaap_EarningsPerShareDiluted	$ 0.54us-gaap_EarningsPerShareDiluted	$ 3.2us-gaap_EarningsPerShareDiluted	$ 2.56us-gaap_EarningsPerShareDiluted	$ 2.28us-gaap_EarningsPerShareDiluted
Dividends declared per common share	$ 0.225us-gaap_CommonStockDividendsPerShareDeclared	$ 0.225us-gaap_CommonStockDividendsPerShareDeclared	$ 0.225us-gaap_CommonStockDividendsPerShareDeclared	$ 0.225us-gaap_CommonStockDividendsPerShareDeclared	$ 0.195us-gaap_CommonStockDividendsPerShareDeclared	$ 0.195us-gaap_CommonStockDividendsPerShareDeclared	$ 0.195us-gaap_CommonStockDividendsPerShareDeclared	$ 0.195us-gaap_CommonStockDividendsPerShareDeclared	$ 0.9us-gaap_CommonStockDividendsPerShareDeclared	$ 0.78us-gaap_CommonStockDividendsPerShareDeclared	$ 0.65us-gaap_CommonStockDividendsPerShareDeclared
Change In Income Tax Expense Related To Effectively Settled Uncertain Tax Positions		$ 724cmcsa_ChangeInIncomeTaxExpenseRelatedToEffectivelySettledUncertainTaxPositions

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