v2.4.0.8

Receivables Monetization (Narrative)(Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Monetization programs payable		$ 882
Payments to third-party banks related to the termination of the monetization programs	1,442
Accounts Receivables Monetized And Uncollected At Program Termination Date	1,078
Cash Receipts Collected And Unremitted At Program Termination Date	364
NBCUniversal Media, LLC [Member]
Monetization programs payable		882
Payments to third-party banks related to the termination of the monetization programs	1,442
Accounts Receivables Monetized And Uncollected At Program Termination Date	1,078
Cash Receipts Collected And Unremitted At Program Termination Date	$ 364

X

- Definition

Represents the amount of accounts receivables that had been monetized and remained uncollected as of the date of the termination of the monetization programs.

+ References

No definition available.

+ Details

Name:	cmcsa_AccountsReceivablesMonetizedAndUncollectedAtProgramTerminationDate
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Represents the cash receipts that had been collected and not yet remitted to the banks as of the date of the termination of the monetization programs.

+ References

No definition available.

+ Details

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

X

- Definition

This element represents cash receipts that have not yet been remitted to the monetization program as of the balance sheet date and are recorded within accounts payable and accrued expenses related to trade creditors.

+ References

No definition available.

+ Details

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

X

- Definition

The cash outflow associated with the termination of the Company's monetization programs.

+ References

No definition available.

+ Details

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