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Supplemental Financial Information (Noncash Investing and Financing Activities) (Details) - USD ($) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Oct. 31, 2017 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Supplemental Financial Information [Line Items] |  |  |  |
Capital Costs Incurred But Not Yet Paid |  | $ 1,900,000,000 | $ 2,100,000,000 | $ 1,200,000,000
Dividends payable |  | $ 956,000,000 | $ 860,000,000 | $ 732,000,000
Dividends payable (in dollars per share) |  | $ 0.21 | $ 0.19 | $ 0.1575
NBCUniversal Media LLC [Member] |  |  |  |
Supplemental Financial Information [Line Items] |  |  |  |
Capital Costs Incurred But Not Yet Paid |  | $ 866,000,000 | $ 1,400,000,000 | $ 325,000,000
Universal Beijing Resort [Member] |  |  |  |
Supplemental Financial Information [Line Items] |  |  |  |
Assets contributed to variable interest entity |  |  | 391,000,000 |
Universal Beijing Resort [Member] | NBCUniversal Media LLC [Member] |  |  |  |
Supplemental Financial Information [Line Items] |  |  |  |
Assets contributed to variable interest entity |  |  | $ 391,000,000 |
Comcast and NBCUniversal Senior Notes [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] |  |  |  |
Supplemental Financial Information [Line Items] |  |  |  |
Aggregate principal amount issued |  |  |  | 5,500,000,000
Aggregate principal amount of certain series of outstanding notes |  |  |  | $ 3,900,000,000
Comcast and NBCUniversal Senior Notes [Member] | Senior Notes Exchange [Member] | Senior Notes [Member] | NBCUniversal Media LLC [Member] |  |  |  |
Supplemental Financial Information [Line Items] |  |  |  |
Aggregate principal amount of certain series of outstanding notes | $ 3,900,000,000 |  |  |

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