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Revenue (Revenue by Geographic Location) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 21,735	$ 21,286	$ 44,526	$ 41,873
United States
Disaggregation of Revenue [Line Items]
Revenue	19,931	19,073	40,816	37,905
Foreign
Disaggregation of Revenue [Line Items]
Revenue	1,804	2,213	3,710	3,968
NBCUniversal Media LLC [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,313	8,318	17,843	16,171
NBCUniversal Media LLC [Member] | United States
Disaggregation of Revenue [Line Items]
Revenue	6,533	6,139	14,187	12,256
NBCUniversal Media LLC [Member] | Foreign
Disaggregation of Revenue [Line Items]
Revenue	$ 1,780	$ 2,179	$ 3,656	$ 3,915

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No definition available.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

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