v3.25.2
Cover Page - shares
 6 Months Ended
Jun. 30, 2025
Jul. 15, 2025
Document And Entity Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-32871  
Entity Registrant Name COMCAST CORPORATION  
Entity Tax Identification Number 27-0000798  
Entity Incorporation, State or Country Code PA  
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  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Document Fiscal Year Focus 2025  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0001166691  
Class A Common Stock, $0.01 par value    
Document And Entity Information [Line Items]    
Title of 12(b) Security Class A Common Stock, $0.01 par value  
Trading Symbol CMCSA  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   3,682,762,127
0.000% Notes due 2026    
Document And Entity Information [Line Items]    
Title of 12(b) Security 0.000% Notes due 2026  
Trading Symbol CMCS26  
Security Exchange Name NASDAQ  
0.250% Notes due 2027    
Document And Entity Information [Line Items]    
Title of 12(b) Security 0.250% Notes due 2027  
Trading Symbol CMCS27  
Security Exchange Name NASDAQ  
1.500% Notes due 2029    
Document And Entity Information [Line Items]    
Title of 12(b) Security 1.500% Notes due 2029  
Trading Symbol CMCS29  
Security Exchange Name NASDAQ  
0.250% Notes due 2029    
Document And Entity Information [Line Items]    
Title of 12(b) Security 0.250% Notes due 2029  
Trading Symbol CMCS29A  
Security Exchange Name NASDAQ  
0.750% Notes due 2032    
Document And Entity Information [Line Items]    
Title of 12(b) Security 0.750% Notes due 2032  
Trading Symbol CMCS32  
Security Exchange Name NASDAQ  
3.250% Notes due 2032    
Document And Entity Information [Line Items]    
Title of 12(b) Security 3.250% Notes due 2032  
Trading Symbol CMCS32A  
Security Exchange Name NASDAQ  
1.875% Notes due 2036    
Document And Entity Information [Line Items]    
Title of 12(b) Security 1.875% Notes due 2036  
Trading Symbol CMCS36  
Security Exchange Name NASDAQ  
3.550% Notes due 2036    
Document And Entity Information [Line Items]    
Title of 12(b) Security 3.550% Notes due 2036  
Trading Symbol CMCS36A  
Security Exchange Name NASDAQ  
1.250% Notes due 2040    
Document And Entity Information [Line Items]    
Title of 12(b) Security 1.250% Notes due 2040  
Trading Symbol CMCS40  
Security Exchange Name NASDAQ  
5.250% Notes due 2040    
Document And Entity Information [Line Items]    
Title of 12(b) Security 5.250% Notes due 2040  
Trading Symbol CMCS40A  
Security Exchange Name NASDAQ  
5.50% Notes due 2029    
Document And Entity Information [Line Items]    
Title of 12(b) Security 5.50% Notes due 2029  
Trading Symbol CCGBP29  
Security Exchange Name NYSE  
2.0% Exchangeable Subordinated Debentures due 2029    
Document And Entity Information [Line Items]    
Title of 12(b) Security 2.0% Exchangeable Subordinated Debentures due 2029  
Trading Symbol CCZ  
Security Exchange Name NYSE  
Class B Common Stock    
Document And Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   9,444,375