Employee Benefit Plans (Deferred Compensation Plans) (Details) - Deferred Compensation Plans [Member] - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | |||
| Benefit obligation | $ 3,273 | $ 2,885 | $ 2,539 |
| Interest expense | 285 | 222 | 209 |
| NBCUniversal Media LLC [Member] | |||
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | |||
| Benefit obligation | 858 | 719 | 621 |
| Interest expense | $ 99 | $ 58 | $ 64 |