Related Party Transactions (Condensed Consolidated Statement of Income) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2019 |
Sep. 30, 2019 |
Jun. 30, 2019 |
Mar. 31, 2019 |
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Related Party Transaction [Line Items] | |||||||||||
| Revenue | $ 28,398 | $ 26,827 | $ 26,858 | $ 26,859 | $ 27,846 | $ 22,135 | $ 21,735 | $ 22,791 | $ 108,942 | $ 94,507 | $ 85,029 |
| Total costs and expenses | (87,817) | (75,498) | (67,011) | ||||||||
| NBCUniversal Media LLC [Member] | |||||||||||
| Related Party Transaction [Line Items] | |||||||||||
| Revenue | 34,021 | 35,895 | 32,950 | ||||||||
| Total costs and expenses | (27,395) | (29,229) | (26,473) | ||||||||
| Comcast and Consolidated Subsidiaries [Member] | NBCUniversal Media LLC [Member] | |||||||||||
| Related Party Transaction [Line Items] | |||||||||||
| Revenue | 2,398 | 2,156 | 1,837 | ||||||||
| Total costs and expenses | (287) | (245) | (214) | ||||||||
| Interest expense and investment and other income (loss), net | $ (133) | $ (54) | $ (250) | ||||||||