Condensed Consolidating Financial Information (Narrative) (Details) $ in Millions |
9 Months Ended |
|---|---|
|
Sep. 30, 2015
USD ($)
| |
| Comcast Holdings' ZONES due October 2029 [Member] | |
| Debt Instrument, Maturity Date, Description | October 2029 |
| Principal amount of debt securities subject to guarantee | $ 185 |
| Comcast Holdings' ZONES due November 2029 [Member] | |
| Debt Instrument, Maturity Date, Description | November 2029 |
| Principal amount of debt securities not subject to guarantee | $ 62 |
| NBCUniversal Enterprise Credit Facility [Member] | |
| Debt Instrument, Maturity Date, Description | March 2018 |
| Principal amount of debt securities subject to guarantee | $ 1,350 |
| Comcast And Comcast Cable Communications, LLC Revolving Credit Facility [Member] | |
| Debt Instrument, Maturity Date, Description | June 2017 |
| Principal amount of debt securities subject to guarantee | $ 6,250 |
| NBCUniversal Enterprise Senior Debt Securities [Member] | |
| Principal amount of debt securities subject to guarantee | $ 4,000 |