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Investments (Schedule of Investments) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Equity method	$ 4,960	$ 4,035
Marketable equity securities	538	341
Nonmarketable equity securities	1,942	1,805
Other investments	1,805	1,796
Total investments	9,245	7,977
Less: Current investments	86	94
Noncurrent investments	9,159	7,883
NBCUniversal Media LLC [Member]
Schedule of Investments [Line Items]
Equity method	831	707
Marketable equity securities	324	162
Nonmarketable equity securities	912	811
Total investments	2,067	1,680
Noncurrent investments	$ 2,067	$ 1,680

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