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Investments (Investment and Other Income (Loss), Net) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investment and Other Income (Loss), Net [Line Items]
Equity in net income (losses) of investees, net	$ 69	$ 15	$ 20	$ 51
Realized and unrealized gains (losses) on equity securities, net	(40)	(2)	(12)	(7)
Other income (loss), net	48	86	195	185
Investment and other income (loss), net	77	99	203	229
NBCUniversal Media LLC [Member]
Investment and Other Income (Loss), Net [Line Items]
Equity in net income (losses) of investees, net	(87)	(29)	(187)	(55)
Realized and unrealized gains (losses) on equity securities, net	(74)	0	(37)	2
Other income (loss), net	(7)	14	52	37
Investment and other income (loss), net	$ (168)	$ (15)	$ (172)	$ (16)

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Nonoperating income (losses), net recorded in the income statement that are not separately stated.

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Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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