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Supplemental Financial Information (Noncash Investing and Financing Activities)(Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares
Supplemental Financial Information [Line Items]
Property and equipment and intangible assets accrued but not yet paid	$ 2,100
Dividends payable	$ 871
Dividends payable (in dollars per share) | $ / shares	$ 0.19
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Property and equipment and intangible assets accrued but not yet paid	$ 1,200
Universal Beijing Resort [Member]
Supplemental Financial Information [Line Items]
Assets contributed to variable interest entity	391
Universal Beijing Resort [Member] | NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Assets contributed to variable interest entity	$ 391

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