Contribution of a business from member

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

+ References

No definition available.

+ Details

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

+ Details

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- Definition

The cash outflow associated with the purchase of noncontrolling interest during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

+ Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=cmcsa_DreamworksAnimationMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=cmcsa_UniversalStudiosJapanMember
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- Details

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- Details

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- Details

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- Details

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- Details

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Significant Transactions (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Apr. 06, 2017	Aug. 22, 2016	Mar. 31, 2017
DreamWorks Animation [Member]
Business Acquisition [Line Items]
Cash consideration transferred		$ 3,773
Business acquisition, price paid per share (in dollars per share)		$ 41
Universal Studios Japan [Member] \| Subsequent Event [Member]
Business Acquisition [Line Items]
Payments to acquire additional interest in noncontrolling interest	$ 2,300
NBCUniversal Media LLC [Member]
Business Acquisition [Line Items]
Contribution from member			$ 662
NBCUniversal Media LLC [Member] \| DreamWorks Animation [Member]
Business Acquisition [Line Items]
Cash consideration transferred		$ 3,773
NBCUniversal Media LLC [Member] \| DreamWorks Animation [Member] \| Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Member]
Business Acquisition [Line Items]
Contribution from member		281
NBCUniversal Media LLC [Member] \| DreamWorks Animation [Member] \| Tax Receivable Agreement [Member]
Business Acquisition [Line Items]
Contribution from member		146
NBCUniversal Media LLC [Member] \| DreamWorks Animation [Member] \| Cash Consideration Transferred By Comcast [Member]
Business Acquisition [Line Items]
Cash consideration transferred		$ 3,773
Business acquisition, price paid per share (in dollars per share)		$ 41
NBCUniversal Media LLC [Member] \| Universal Studios Japan [Member] \| Subsequent Event [Member]
Business Acquisition [Line Items]
Payments to acquire additional interest in noncontrolling interest	$ 2,300