Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash and cash equivalents	$ 3,910,000,000	$ 1,718,000,000	$ 10,951,000,000	$ 1,620,000,000
Investments [Current]	602,000,000us-gaap_ShortTermInvestments	3,573,000,000us-gaap_ShortTermInvestments
Receivables, net	6,321,000,000us-gaap_AccountsReceivableNetCurrent	6,376,000,000us-gaap_AccountsReceivableNetCurrent
Programming rights	839,000,000cmcsa_ProgrammingRightsCurrent	928,000,000cmcsa_ProgrammingRightsCurrent
Other current assets	1,859,000,000us-gaap_OtherAssetsCurrent	1,480,000,000us-gaap_OtherAssetsCurrent
Total current assets	13,531,000,000us-gaap_AssetsCurrent	14,075,000,000us-gaap_AssetsCurrent
Film and television costs	5,727,000,000cmcsa_FilmAndTelevisionCosts	4,994,000,000cmcsa_FilmAndTelevisionCosts
Investments	3,135,000,000us-gaap_LongTermInvestments	3,770,000,000us-gaap_LongTermInvestments
Property and equipment, net	30,953,000,000us-gaap_PropertyPlantAndEquipmentNet	29,840,000,000us-gaap_PropertyPlantAndEquipmentNet
Franchise rights	59,364,000,000us-gaap_IndefiniteLivedFranchiseRights	59,364,000,000us-gaap_IndefiniteLivedFranchiseRights
Goodwill	27,316,000,000us-gaap_Goodwill	27,098,000,000us-gaap_Goodwill	26,985,000,000us-gaap_Goodwill
Other intangible assets, net	16,980,000,000us-gaap_OtherIntangibleAssetsNet	17,329,000,000us-gaap_OtherIntangibleAssetsNet
Other noncurrent assets, net	2,333,000,000us-gaap_OtherAssetsNoncurrent	2,343,000,000us-gaap_OtherAssetsNoncurrent
Total assets	159,339,000,000us-gaap_Assets	158,813,000,000us-gaap_Assets
Accounts payable and accrued expenses related to trade creditors	5,638,000,000us-gaap_AccountsPayableCurrent	5,528,000,000us-gaap_AccountsPayableCurrent
Accrued participations and residuals	1,347,000,000	1,239,000,000
Accrued expenses and other current liabilities [condensed]	6,208,000,000	8,865,000,000
Current portion of long-term debt	4,217,000,000us-gaap_DebtCurrent	3,280,000,000us-gaap_DebtCurrent
Total current liabilities	17,410,000,000us-gaap_LiabilitiesCurrent	18,912,000,000us-gaap_LiabilitiesCurrent
Long-term debt, less current portion	44,017,000,000	44,567,000,000
Deferred income taxes	32,959,000,000	31,935,000,000
Other noncurrent liabilities	10,819,000,000us-gaap_OtherLiabilitiesNoncurrent	11,384,000,000us-gaap_OtherLiabilitiesNoncurrent
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,066,000,000	957,000,000
Common stock	30,000,000us-gaap_CommonStockValue	30,000,000us-gaap_CommonStockValue
Other shareholders' equity	52,681,000,000cmcsa_OtherStockholdersEquity	50,664,000,000cmcsa_OtherStockholdersEquity
Total Comcast Corporation shareholders' equity	52,711,000,000us-gaap_StockholdersEquity	50,694,000,000us-gaap_StockholdersEquity
Noncontrolling interests	357,000,000us-gaap_MinorityInterest	364,000,000us-gaap_MinorityInterest
Total equity	53,068,000,000	51,058,000,000	49,796,000,000	47,655,000,000
Total liabilities and equity	159,339,000,000	158,813,000,000
Elimination and Consolidation Adjustments [Member]
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	(495,953,000,000)	(460,590,000,000)
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	(1,080,000,000)	(882,000,000)
Total assets	(497,033,000,000)	(461,472,000,000)
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	0	0
Current portion of long-term debt	0	0
Total current liabilities	0	0
Long-term debt, less current portion	0	0
Deferred income taxes	(936,000,000)	(741,000,000)
Other noncurrent liabilities	(144,000,000)	(141,000,000)
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	(495,953,000,000)	(460,590,000,000)
Total Comcast Corporation shareholders' equity	(495,953,000,000)	(460,590,000,000)
Noncontrolling interests	0	0
Total equity	(495,953,000,000)	(460,590,000,000)
Total liabilities and equity	(497,033,000,000)	(461,472,000,000)
Comcast Parent [Member]
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	267,000,000	237,000,000
Total current assets	267,000,000	237,000,000
Film and television costs	0	0
Investments	36,000,000	11,000,000
Investments in and amounts due from subsidiaries eliminated upon consolidation	84,142,000,000	79,956,000,000
Property and equipment, net	199,000,000	220,000,000
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	11,000,000	11,000,000
Other noncurrent assets, net	1,224,000,000	1,078,000,000
Total assets	85,879,000,000	81,513,000,000
Accounts payable and accrued expenses related to trade creditors	19,000,000	8,000,000
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	1,547,000,000	1,371,000,000
Current portion of long-term debt	1,650,000,000	2,351,000,000
Total current liabilities	3,216,000,000	3,730,000,000
Long-term debt, less current portion	27,616,000,000	25,170,000,000
Deferred income taxes	0	0
Other noncurrent liabilities	2,336,000,000	1,919,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	30,000,000	30,000,000
Other shareholders' equity	52,681,000,000	50,664,000,000
Total Comcast Corporation shareholders' equity	52,711,000,000	50,694,000,000
Noncontrolling interests	0	0
Total equity	52,711,000,000	50,694,000,000
Total liabilities and equity	85,879,000,000	81,513,000,000
Comcast Holdings [Member]
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	103,420,000,000	97,429,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	148,000,000	145,000,000
Total assets	103,568,000,000	97,574,000,000
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	283,000,000	266,000,000
Current portion of long-term debt	0	0
Total current liabilities	283,000,000	266,000,000
Long-term debt, less current portion	126,000,000	132,000,000
Deferred income taxes	701,000,000	777,000,000
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	102,458,000,000	96,399,000,000
Total Comcast Corporation shareholders' equity	102,458,000,000	96,399,000,000
Noncontrolling interests	0	0
Total equity	102,458,000,000	96,399,000,000
Total liabilities and equity	103,568,000,000	97,574,000,000
CCCL Parent [Member]
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	110,323,000,000	102,673,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	0	0
Total assets	110,323,000,000	102,673,000,000
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	233,000,000	180,000,000
Current portion of long-term debt	0	0
Total current liabilities	233,000,000	180,000,000
Long-term debt, less current portion	1,827,000,000	1,827,000,000
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	108,263,000,000	100,666,000,000
Total Comcast Corporation shareholders' equity	108,263,000,000	100,666,000,000
Noncontrolling interests	0	0
Total equity	108,263,000,000	100,666,000,000
Total liabilities and equity	110,323,000,000	102,673,000,000
Combined CCHMO Parents [Member]
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	0	0
Total current assets	0	0
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	58,677,000,000	54,724,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	0	0
Total assets	58,677,000,000	54,724,000,000
Accounts payable and accrued expenses related to trade creditors	1,000,000	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	47,000,000	47,000,000
Current portion of long-term debt	677,000,000	0
Total current liabilities	725,000,000	47,000,000
Long-term debt, less current portion	822,000,000	1,505,000,000
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	57,130,000,000	53,172,000,000
Total Comcast Corporation shareholders' equity	57,130,000,000	53,172,000,000
Noncontrolling interests	0	0
Total equity	57,130,000,000	53,172,000,000
Total liabilities and equity	58,677,000,000	54,724,000,000
NBCUniversal Media Parent [Member]
Cash and cash equivalents	385,000,000	336,000,000	5,129,000,000	238,000,000
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	41,000,000	35,000,000
Total current assets	426,000,000	371,000,000
Film and television costs	0	0
Investments	378,000,000	374,000,000
Investments in and amounts due from subsidiaries eliminated upon consolidation	41,239,000,000	40,644,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	92,000,000	103,000,000
Total assets	42,135,000,000	41,492,000,000
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	331,000,000	323,000,000
Current portion of long-term debt	1,006,000,000	903,000,000
Total current liabilities	1,337,000,000	1,226,000,000
Long-term debt, less current portion	9,218,000,000	10,236,000,000
Deferred income taxes	67,000,000	59,000,000
Other noncurrent liabilities	1,143,000,000	931,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	30,370,000,000	29,040,000,000
Total Comcast Corporation shareholders' equity	30,370,000,000	29,040,000,000
Noncontrolling interests	0	0
Total equity	30,370,000,000	29,040,000,000
Total liabilities and equity	42,135,000,000	41,492,000,000
Comcast Non-Guarantor Subsidiaries [Member]
Cash and cash equivalents	3,525,000,000	1,382,000,000	5,822,000,000	1,382,000,000
Investments [Current]	602,000,000	3,573,000,000
Receivables, net	6,321,000,000	6,376,000,000
Programming rights	839,000,000	928,000,000
Other current assets	1,551,000,000	1,208,000,000
Total current assets	12,838,000,000	13,467,000,000
Film and television costs	5,727,000,000	4,994,000,000
Investments	2,721,000,000	3,385,000,000
Investments in and amounts due from subsidiaries eliminated upon consolidation	98,152,000,000	85,164,000,000
Property and equipment, net	30,754,000,000	29,620,000,000
Franchise rights	59,364,000,000	59,364,000,000
Goodwill	27,316,000,000	27,098,000,000
Other intangible assets, net	16,969,000,000	17,318,000,000
Other noncurrent assets, net	1,949,000,000	1,899,000,000
Total assets	255,790,000,000	242,309,000,000
Accounts payable and accrued expenses related to trade creditors	5,618,000,000	5,520,000,000
Accrued participations and residuals	1,347,000,000	1,239,000,000
Accrued expenses and other current liabilities [condensed]	3,767,000,000	6,678,000,000
Current portion of long-term debt	884,000,000	26,000,000
Total current liabilities	11,616,000,000	13,463,000,000
Long-term debt, less current portion	4,408,000,000	5,697,000,000
Deferred income taxes	33,127,000,000	31,840,000,000
Other noncurrent liabilities	7,484,000,000	8,675,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,066,000,000	957,000,000
Common stock	0	0
Other shareholders' equity	197,732,000,000	181,313,000,000
Total Comcast Corporation shareholders' equity	197,732,000,000	181,313,000,000
Noncontrolling interests	357,000,000	364,000,000
Total equity	198,089,000,000	181,677,000,000
Total liabilities and equity	$ 255,790,000,000	$ 242,309,000,000

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The total amount of participations, residual and royalty expenses due to another party in less than one year. Royalty expenses are due to content creators, including artists, authors and other talent; participations includes amounts to financial participants in films, including actors, directors, and producers, for contractually defined participations in a film's net profit or gross receipts; residuals include amounts due to unions and guilds.

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Other stockholders equity.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable and the carrying amount attributable to a subsidiary entity's issued and outstanding preferred stock, which are not included within permanent equity or liabilities.

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Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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