Document and Entity Information	6 Months Ended
	Jun. 30, 2011
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2011
Document Fiscal Year Focus	2011
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
Class A Common Stock [Member]
Entity Common Stock, Shares Outstanding	2,089,624,288
Class A Special Common Stock [Member]
Entity Common Stock, Shares Outstanding	650,044,422
Class B Common Stock [Member]
Entity Common Stock, Shares Outstanding	9,444,375