Revenue (Revenue by Geographic Location) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Disaggregation of Revenue [Line Items] | |||||||||||
| Revenue | $ 27,846 | $ 22,135 | $ 21,735 | $ 22,791 | $ 22,075 | $ 21,081 | $ 21,286 | $ 20,587 | $ 94,507 | $ 85,029 | $ 80,736 |
| United States [Member] | |||||||||||
| Disaggregation of Revenue [Line Items] | |||||||||||
| Revenue | 82,233 | 77,246 | 74,212 | ||||||||
| Foreign [Member] | |||||||||||
| Disaggregation of Revenue [Line Items] | |||||||||||
| Revenue | 12,274 | 7,783 | 6,524 | ||||||||
| NBCUniversal Media LLC [Member] | |||||||||||
| Disaggregation of Revenue [Line Items] | |||||||||||
| Revenue | 35,895 | 32,950 | 31,398 | ||||||||
| NBCUniversal Media LLC [Member] | United States [Member] | |||||||||||
| Disaggregation of Revenue [Line Items] | |||||||||||
| Revenue | 28,309 | 25,303 | 24,907 | ||||||||
| NBCUniversal Media LLC [Member] | Foreign [Member] | |||||||||||
| Disaggregation of Revenue [Line Items] | |||||||||||
| Revenue | $ 7,586 | $ 7,647 | $ 6,491 | ||||||||