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Revenue (Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Condensed Consolidated Balance Sheet [Line Items] |  |
Receivables, gross | $ 9,142 | $ 9,122
Less: Allowance for doubtful accounts | 295 | 288
Receivables, net | 8,847 | 8,834
NBCUniversal Media LLC [Member] |  |
Condensed Consolidated Balance Sheet [Line Items] |  |
Receivables, gross | 7,097 | 7,055
Less: Allowance for doubtful accounts | 95 | 88
Receivables, net | 7,002 | 6,967
Accounting Standards Update 2014-09 [Member] |  |
Condensed Consolidated Balance Sheet [Line Items] |  |
Noncurrent receivables, net (included in other noncurrent assets, net) | 1,191 | 1,184
Contract acquisition and fulfillment costs (included in other noncurrent assets, net) | 929 | 922
Noncurrent deferred revenue (included in other noncurrent liabilities) | 530 | 497
Accounting Standards Update 2014-09 [Member] | NBCUniversal Media LLC [Member] |  |
Condensed Consolidated Balance Sheet [Line Items] |  |
Noncurrent receivables, net (included in other noncurrent assets, net) | 1,091 | 1,093
Noncurrent deferred revenue (included in other noncurrent liabilities) | $ 424 | $ 392

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