Goodwill and Intangible Assets (Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Franchise rights	$ 59,364us-gaap_IndefiniteLivedFranchiseRights	$ 59,364us-gaap_IndefiniteLivedFranchiseRights
Accumulated amortization	(10,170)	(8,874)
Total	86,514	85,567
NBCUniversal Media, LLC [Member]
Accumulated amortization	(4,829)	(4,003)
Total	19,016	18,860
Trade names
Indefinite Lived Intangible Assets Excluding Goodwill	3,083	3,089
Trade names \| NBCUniversal Media, LLC [Member]
Indefinite Lived Intangible Assets Excluding Goodwill	3,059	3,089
FCC Licenses
Indefinite Lived Intangible Assets Excluding Goodwill	651	652
FCC Licenses \| NBCUniversal Media, LLC [Member]
Indefinite Lived Intangible Assets Excluding Goodwill	651	652
Customer relationships
Finite-lived intangible assets, gross carrying amount	15,129	15,037
Accumulated amortization	(5,495)	(4,772)
Weighted average original useful life	19 years 0 months 0 days
Customer relationships \| NBCUniversal Media, LLC [Member]
Finite-lived intangible assets, gross carrying amount	13,093	13,086
Accumulated amortization	(3,636)	(2,982)
Weighted average original useful life	19 years 0 months 0 days
Cable franchise renewal costs and contractual operating rights
Finite-lived intangible assets, gross carrying amount	1,418	1,360
Accumulated amortization	(792)	(745)
Weighted average original useful life	10 years 0 months 0 days
Software
Finite-lived intangible assets, gross carrying amount	5,040	4,271
Accumulated amortization	(2,832)	(2,405)
Weighted average original useful life	5 years 0 months 0 days
Software \| NBCUniversal Media, LLC [Member]
Finite-lived intangible assets, gross carrying amount	657	522
Accumulated amortization	(329)	(240)
Weighted average original useful life	5 years 0 months 0 days
Patents and other technology rights
Finite-lived intangible assets, gross carrying amount	373	361
Accumulated amortization	(330)	(307)
Weighted average original useful life	8 years 0 months 0 days
Other agreements and rights
Finite-lived intangible assets, gross carrying amount	1,456	1,433
Accumulated amortization	(721)	(645)
Weighted average original useful life	20 years 0 months 0 days
Other agreements and rights \| NBCUniversal Media, LLC [Member]
Finite-lived intangible assets, gross carrying amount	1,556	1,511
Accumulated amortization	$ (864)	$ (781)
Weighted average original useful life	21 years 0 months 0 days

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Carrying amount (original costs adjusted for previously recognized amortization and impairment) as of the balance sheet date for the rights acquired through a franchise arrangement having an indefinite period of benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount before accumulated amortization of intangible assets, excluding goodwill.

+ References

No definition available.

+ Details

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