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Related Party Transactions (Condensed Consolidated Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Related Party Transaction [Line Items]
Revenue	$ 21,735	$ 21,286	$ 44,526	$ 41,873
Total costs and expenses	(16,721)	(16,718)	(34,867)	(32,763)
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Revenue	8,313	8,318	17,843	16,171
Total costs and expenses	(6,706)	(6,764)	(14,461)	(13,106)
Comcast and Consolidated Subsidiaries [Member] | NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Revenue	480	460	1,074	919
Total costs and expenses	(42)	(49)	(103)	(110)
Interest expense and investment and other income (loss), net	$ (20)	$ (28)	$ (43)	$ (47)

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Represents the intercompany transactions with ultimate parent, which are included in interest expense and investment and other income (loss), net.

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