Document and Entity Information	6 Months Ended
	Jun. 30, 2014
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q2
Trading Symbol	cmcsa
Entity Registrant Name	COMCAST CORP
Entity Central Index Key	0001166691
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
NBCUniversal Media, LLC [Member]
Amendment Flag	false
Entity Registrant Name	NBCUniversal Media, LLC
Entity Central Index Key	0000902739
Entity Filer Category	Non-accelerated Filer
Class A Common Stock [Member]
Entity Common Stock, Shares Outstanding	2,149,576,442
ClassA Special Common Stock [Member]
Entity Common Stock, Shares Outstanding	429,082,218
Class B Common Stock [Member]
Entity Common Stock, Shares Outstanding	9,444,375