v2.4.0.8
Long-Term Debt (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Long-term Debt, Fair Value $ 51,800,000,000 $ 47,700,000,000  
Revolving credit facilities 1,250,000,000    
Amounts available under revolving credit facilities 4,700,000,000    
Repurchases and repayments of debt 2,444,000,000 2,881,000,000 3,216,000,000
Unused irrevocable standby letters of credit 515,000,000    
Commercial paper prior borrowing capacity [Member]
     
Credit facility borrowing capacity 2,250,000,000    
NBCUniversal Media, LLC [Member]
     
Long-term Debt, Fair Value 11,700,000,000 12,600,000,000  
NBCUniversal Enterprise Senior Unsecured Debt Securities
     
Consideration transferred related to the Redemption Transaction and purchase of certain properties 4,000,000,000    
Comcast Commercial Paper Program
     
Consideration transferred related to the Redemption Transaction and purchase of certain properties 750,000,000    
NBCUniversal Enterprise Credit Facility
     
Consideration transferred related to the Redemption Transaction and purchase of certain properties 1,250,000,000    
Amounts available under revolving credit facilities 100,000,000    
Comcast And Comcast Cable Communications LLC [Member]
     
Debt Instrument, Maturity Date, Description June 2017    
Credit facility borrowing capacity 6,250,000,000    
Comcast And Comcast Cable Communications LLC [Member] | NBCUniversal Media, LLC [Member]
     
Debt Instrument, Maturity Date, Description June 2017    
Credit facility borrowing capacity 6,250,000,000    
Guarantee Obligations Current Principal Balance 31,000,000,000    
NBCUniversal Enterprise [Member] | NBCUniversal Media, LLC [Member]
     
Principal amount 4,000,000,000    
Preferred stock liquidition preference value 725,000,000    
Senior 1.662% Notes Due 2018 [Member] | NBCUniversal Enterprise [Member]
     
Principal amount 1,100,000,000    
Interest rate 1.662%    
Debt Instrument, Maturity Date, Description 2018    
Senior 1.974% Notes Due 2019 [Member] | NBCUniversal Enterprise [Member]
     
Principal amount 1,500,000,000    
Interest rate 1.974%    
Debt Instrument, Maturity Date, Description 2019    
Floating Rate Senior Notes Due 2018 [Member] | NBCUniversal Enterprise [Member]
     
Principal amount 700,000,000    
Debt Instrument, Maturity Date, Description 2018    
Spread above LIBOR offered rate 0.685%    
Floating Rate Senior Notes Due 2016 [Member] | NBCUniversal Enterprise [Member]
     
Principal amount 700,000,000    
Debt Instrument, Maturity Date, Description 2016    
Spread above LIBOR offered rate 0.537%    
Other Long-Term Debt [Member]
     
Repurchases and repayments of debt 109,000,000    
Notes 5.50% Due 2029 [Member]
     
Interest rate 5.50% 5.50%  
Debt Instrument, Maturity Date, Description 2029 2029  
Senior 2.850% Notes Due 2023 [Member]
     
Principal amount 750,000,000    
Interest rate 2.85%    
Debt Instrument, Maturity Date, Description 2023    
Senior 4.250% Notes Due 2033 [Member]
     
Principal amount 1,700,000,000    
Interest rate 4.25%    
Debt Instrument, Maturity Date, Description 2033    
Senior 4.500% Notes Due 2043 [Member]
     
Principal amount 500,000,000    
Interest rate 4.50%    
Debt Instrument, Maturity Date, Description 2043    
Current Year Borrowings [Member]
     
Principal amount 2,950,000,000    
Prior NBCUniversal Credit Facility [Member]
     
Credit facility borrowing capacity 1,500,000,000    
NBCUniversal Enterprise Credit Facility [Member]
     
Debt Instrument, Maturity Date, Description March 2018    
Credit facility borrowing capacity 1,350,000,000    
NBCUniversal Enterprise Credit Facility [Member] | NBCUniversal Media, LLC [Member]
     
Credit facility borrowing capacity 1,350,000,000    
Senior 8.375% Notes Due 2013 [Member]
     
Interest rate 8.375%    
Debt Instrument, Maturity Date, Description 2013    
Repurchases and repayments of debt 1,714,000,000    
Senior 7.125% Notes Due 2013 [Member]
     
Interest rate 7.125%    
Debt Instrument, Maturity Date, Description 2013    
Repurchases and repayments of debt 383,000,000    
Senior 7.875% Notes Due 2013 [Member]
     
Interest rate 7.875%    
Debt Instrument, Maturity Date, Description 2013    
Repurchases and repayments of debt $ 238,000,000