Condensed Consolidating Financial Information (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)
Comcast Holdings' ZONES due October 2029 [Member]
Debt Instrument, Maturity Date, Description	October 2029
Principal amount of debt securities subject to guarantee	$ 185
Comcast Holdings' ZONES due November 2029 [Member]
Debt Instrument, Maturity Date, Description	November 2029
Principal amount of debt securities not subject to guarantee	$ 62
NBCUniversal Enterprise Senior Debt Securities [Member]
Principal amount of debt securities subject to guarantee	3,300
Universal Studios Japan Term Loans [Member]
Principal amount of debt securities not subject to guarantee	$ 3,800