Related Party Transactions (Condensed Consolidated Statement of Income) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Related Party Transaction [Line Items] | |||||||||||
| Revenue | $ 21,025 | $ 21,319 | $ 19,269 | $ 18,790 | $ 19,245 | $ 18,669 | $ 18,743 | $ 17,853 | $ 80,403 | $ 74,510 | $ 68,775 |
| NBCUniversal Media LLC [Member] | |||||||||||
| Related Party Transaction [Line Items] | |||||||||||
| Revenue | 31,593 | 28,462 | 25,428 | ||||||||
| Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media LLC [Member] | |||||||||||
| Related Party Transaction [Line Items] | |||||||||||
| Revenue | 1,742 | 1,349 | 1,315 | ||||||||
| Operating costs and expenses | (220) | (246) | (162) | ||||||||
| Other income (expense) | $ (69) | $ (37) | $ (43) | ||||||||