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Supplemental Financial Information (Noncash Activities) (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares
Supplemental Financial Information [Line Items]
Property and equipment and intangible assets accrued but not yet paid	$ 1,600
Dividends payable	$ 953
Dividends payable (in dollars per share) | $ / shares	$ 0.21
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Property and equipment and intangible assets accrued but not yet paid	$ 633

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[Line Items] for Supplemental Financial Information [Table]

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Future cash outflow to pay for purchases of fixed assets that have occurred.

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