Carrying amount of redeemable preferred stock

No definition available.

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Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of Preferred Stock Series

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for repurchase and redemption of subsidiary preferred stock.

+ References

No definition available.

+ Details

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Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment in debt security measured at amortized cost (held-to-maturity), classified as current.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26626-111562

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with the maturity, prepayments and calls (requests for early payments) of debt securities designated as held-to-maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26853-111562

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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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- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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- Details

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Investments (Other Investments) (Details) $ in Billions	1 Months Ended
Investments (Other Investments) (Details) $ in Billions	Apr. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) preferred_stock_series	Dec. 31, 2019 USD ($)
Subsequent Event [Member]
Schedule of Other Investments [Line Items]
Cash payments for the redemption of redeemable preferred shares	$ 1.8
Air Touch [Member]
Schedule of Other Investments [Line Items]
Redeemable subsidiary preferred shares		$ 1.7	$ 1.7
Air Touch [Member]
Schedule of Other Investments [Line Items]
Number of series of preferred stock \| preferred_stock_series		2
Held to maturity investment		$ 1.7	$ 1.6
Air Touch [Member] \| Subsequent Event [Member]
Schedule of Other Investments [Line Items]
Cash payments received upon redemption of preferred stock	$ 1.7