v3.20.1
Document and Entity Information
Mar. 27, 2020
Document And Entity Information [Line Items]  
Entity Registrant Name COMCAST CORP
Amendment Flag false
Entity Central Index Key 0001166691
Document Type 8-K
Document Period End Date Mar. 27, 2020
Entity Incorporation State Country Code PA
Entity File Number 001-32871
Entity Tax Identification Number 27-0000798
Entity Address, Address Line One One Comcast Center
Entity Address, City or Town Philadelphia
Entity Address, State or Province PA
Entity Address, Postal Zip Code 19103-2838
City Area Code (215)
Local Phone Number 286-1700
Written Communications false
Soliciting Material false
Pre Commencement Tender Offer false
Pre Commencement Issuer Tender Offer false
Entity Emerging Growth Company false
Common Class A [Member]  
Document And Entity Information [Line Items]  
Security 12b Title Class A Common Stock, $0.01 par value
Trading Symbol CMCSA
Security Exchange Name NASDAQ
M 0.250 Percent Notes Due 2027 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 0.250% Notes due 2027
Trading Symbol CMCS27
Security Exchange Name NASDAQ
M 0.750 Percent Notes Due 2032 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 0.750% Notes due 2032
Trading Symbol CMCS32
Security Exchange Name NASDAQ
M 1.250 Percent Notes Due 2040 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 1.250% Notes due 2040
Trading Symbol CMCS40
Security Exchange Name NASDAQ
M 1.500 Percent Notes Due 2029 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 1.500% Notes due 2029
Trading Symbol CMCS29
Security Exchange Name NASDAQ
M 1.875 Percent Notes Due 2036 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 1.875% Notes due 2036
Trading Symbol CMCS36
Security Exchange Name NASDAQ
Exchangeable Debt [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 2.0% Exchangeable SubordinatedDebentures due 2029
Trading Symbol CCZ
Security Exchange Name NYSE
Notes 550 Due 2029 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 5.50% Notes due 2029
Trading Symbol CCGBP29
Security Exchange Name NYSE
Guaranteed Notes 9455 Percent Due 2022 [Member]  
Document And Entity Information [Line Items]  
Security 12b Title 9.455% Guaranteed Notes due 2022
Trading Symbol CMCSA/22
Security Exchange Name NYSE