Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Cash and cash equivalents	$ 3,937	$ 3,910	$ 3,054	$ 1,718
Investments [Current]	158us-gaap_ShortTermInvestments	602us-gaap_ShortTermInvestments
Receivables, net	6,144us-gaap_AccountsReceivableNetCurrent	6,321us-gaap_AccountsReceivableNetCurrent
Programming rights	945cmcsa_ProgrammingRightsCurrent	839cmcsa_ProgrammingRightsCurrent
Other current assets	1,737us-gaap_OtherAssetsCurrent	1,859us-gaap_OtherAssetsCurrent
Total current assets	12,921us-gaap_AssetsCurrent	13,531us-gaap_AssetsCurrent
Film and television costs	5,637cmcsa_FilmAndTelevisionCosts	5,727cmcsa_FilmAndTelevisionCosts
Investments	3,235us-gaap_LongTermInvestments	3,135us-gaap_LongTermInvestments
Investments in and amounts due from subsidiaries eliminated upon consolidation	0	0
Property and equipment, net	31,127us-gaap_PropertyPlantAndEquipmentNet	30,953us-gaap_PropertyPlantAndEquipmentNet
Franchise rights	59,364us-gaap_IndefiniteLivedFranchiseRights	59,364us-gaap_IndefiniteLivedFranchiseRights
Goodwill	27,302us-gaap_Goodwill	27,316us-gaap_Goodwill
Other intangible assets, net	16,852us-gaap_OtherIntangibleAssetsNet	16,980us-gaap_OtherIntangibleAssetsNet
Other noncurrent assets, net	2,319us-gaap_OtherAssetsNoncurrent	2,333us-gaap_OtherAssetsNoncurrent
Total assets	158,757us-gaap_Assets	159,339us-gaap_Assets
Accounts payable and accrued expenses related to trade creditors	6,157us-gaap_AccountsPayableCurrent	5,638us-gaap_AccountsPayableCurrent
Accrued participations and residuals	1,387	1,347
Accrued expenses and other current liabilities [condensed]	6,778	6,208
Current portion of long-term debt	4,180us-gaap_DebtCurrent	4,217us-gaap_DebtCurrent
Total current liabilities	18,502us-gaap_LiabilitiesCurrent	17,410us-gaap_LiabilitiesCurrent
Long-term debt, less current portion	42,953	44,017
Deferred income taxes	32,855	32,959
Other noncurrent liabilities	10,837us-gaap_OtherLiabilitiesNoncurrent	10,819us-gaap_OtherLiabilitiesNoncurrent
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,099	1,066
Common stock	30us-gaap_CommonStockValue	30us-gaap_CommonStockValue
Other shareholders' equity	52,141cmcsa_OtherStockholdersEquity	52,681cmcsa_OtherStockholdersEquity
Total Comcast Corporation shareholders' equity	52,171us-gaap_StockholdersEquity	52,711us-gaap_StockholdersEquity
Noncontrolling interests	340us-gaap_MinorityInterest	357us-gaap_MinorityInterest
Total equity	52,511	53,068	51,632	51,058
Total liabilities and equity	158,757	159,339
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	279	267
Total current assets	279	267
Film and television costs	0	0
Investments	31	36
Investments in and amounts due from subsidiaries eliminated upon consolidation	82,713	84,142
Property and equipment, net	200	199
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	10	11
Other noncurrent assets, net	1,201	1,224
Total assets	84,434	85,879
Accounts payable and accrued expenses related to trade creditors	7	19
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	1,534	1,547
Current portion of long-term debt	1,761	1,650
Total current liabilities	3,302	3,216
Long-term debt, less current portion	26,566	27,616
Deferred income taxes	0	0
Other noncurrent liabilities	2,395	2,336
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	30	30
Other shareholders' equity	52,141	52,681
Total Comcast Corporation shareholders' equity	52,171	52,711
Noncontrolling interests	0	0
Total equity	52,171	52,711
Total liabilities and equity	84,434	85,879
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	105,551	103,420
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	148	148
Total assets	105,699	103,568
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	283
Current portion of long-term debt	0	0
Total current liabilities	283	283
Long-term debt, less current portion	126	126
Deferred income taxes	682	701
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	104,608	102,458
Total Comcast Corporation shareholders' equity	104,608	102,458
Noncontrolling interests	0	0
Total equity	104,608	102,458
Total liabilities and equity	105,699	103,568
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	112,432	110,323
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	112,432	110,323
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	343	233
Current portion of long-term debt	0	0
Total current liabilities	343	233
Long-term debt, less current portion	1,828	1,827
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	110,261	108,263
Total Comcast Corporation shareholders' equity	110,261	108,263
Noncontrolling interests	0	0
Total equity	110,261	108,263
Total liabilities and equity	112,432	110,323
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	60,289	58,677
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	60,289	58,677
Accounts payable and accrued expenses related to trade creditors	0	1
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	21	47
Current portion of long-term debt	676	677
Total current liabilities	697	725
Long-term debt, less current portion	822	822
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	58,770	57,130
Total Comcast Corporation shareholders' equity	58,770	57,130
Noncontrolling interests	0	0
Total equity	58,770	57,130
Total liabilities and equity	60,289	58,677
NBCUniversal Media Parent [Member]
Cash and cash equivalents	339	385	506	336
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	64	41
Total current assets	403	426
Film and television costs	0	0
Investments	372	378
Investments in and amounts due from subsidiaries eliminated upon consolidation	41,900	41,239
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	97	92
Total assets	42,772	42,135
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	407	331
Current portion of long-term debt	1,003	1,006
Total current liabilities	1,410	1,337
Long-term debt, less current portion	9,217	9,218
Deferred income taxes	67	67
Other noncurrent liabilities	1,103	1,143
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	30,975	30,370
Total Comcast Corporation shareholders' equity	30,975	30,370
Noncontrolling interests	0	0
Total equity	30,975	30,370
Total liabilities and equity	42,772	42,135
Comcast Non-Guarantor Subsidiaries [Member]
Cash and cash equivalents	3,598	3,525	2,548	1,382
Investments [Current]	158	602
Receivables, net	6,144	6,321
Programming rights	945	839
Other current assets	1,394	1,551
Total current assets	12,239	12,838
Film and television costs	5,637	5,727
Investments	2,832	2,721
Investments in and amounts due from subsidiaries eliminated upon consolidation	101,682	98,152
Property and equipment, net	30,927	30,754
Franchise rights	59,364	59,364
Goodwill	27,302	27,316
Other intangible assets, net	16,842	16,969
Other noncurrent assets, net	1,970	1,949
Total assets	258,795	255,790
Accounts payable and accrued expenses related to trade creditors	6,150	5,618
Accrued participations and residuals	1,387	1,347
Accrued expenses and other current liabilities [condensed]	4,190	3,767
Current portion of long-term debt	740	884
Total current liabilities	12,467	11,616
Long-term debt, less current portion	4,394	4,408
Deferred income taxes	33,059	33,127
Other noncurrent liabilities	7,483	7,484
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,099	1,066
Common stock	0	0
Other shareholders' equity	199,953	197,732
Total Comcast Corporation shareholders' equity	199,953	197,732
Noncontrolling interests	340	357
Total equity	200,293	198,089
Total liabilities and equity	258,795	255,790
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	(504,567)	(495,953)
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	(1,097)	(1,080)
Total assets	(505,664)	(497,033)
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	(953)	(936)
Other noncurrent liabilities	(144)	(144)
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	(504,567)	(495,953)
Total Comcast Corporation shareholders' equity	(504,567)	(495,953)
Noncontrolling interests	0	0
Total equity	(504,567)	(495,953)
Total liabilities and equity	$ (505,664)	$ (497,033)

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

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The net carrying amount as of the balance sheet date of other indefinite-lived and finite-lived intangible assets that are not separately presented on the statement of financial position.

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No definition available.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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