v3.7.0.1
Document and Entity Information
3 Months Ended
Mar. 31, 2017
shares
Document And Entity Information [Line Items]  
Document Type 10-Q
Amendment Flag false
Document Period End Date Mar. 31, 2017
Document Fiscal Year Focus 2017
Document Fiscal Period Focus Q1
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]  
Document And Entity Information [Line Items]  
Entity Registrant Name NBCUniversal Media, LLC
Entity Central Index Key 0000902739
Entity Filer Category Non-accelerated Filer
Class A Common Stock [Member]  
Document And Entity Information [Line Items]  
Entity Common Stock, Shares Outstanding 4,733,512,494
Class B Common Stock [Member]  
Document And Entity Information [Line Items]  
Entity Common Stock, Shares Outstanding 9,444,375