Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 1,893	$ 3,910	$ 4,547	$ 1,718
Investments [Current]	137	602
Receivables, net	6,527	6,321
Programming rights	1,130	839
Other current assets	1,814	1,859
Total current assets	11,501	13,531
Film and television costs	5,712	5,727
Investments	3,323	3,135
Investments in and amounts due from subsidiaries eliminated upon consolidation	0	0
Property and equipment, net	32,170	30,953
Franchise rights	59,364	59,364
Goodwill	27,492	27,316
Other intangible assets, net	16,896	16,980
Other noncurrent assets, net	2,500	2,333
Total assets	158,958	159,339
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	5,996	5,638
Accrued participations and residuals	1,491	1,347
Accrued expenses and other current liabilities [condensed]	6,720	6,208
Current portion of long-term debt	3,152	4,217
Total current liabilities	17,359	17,410
Long-term debt, less current portion	44,605	44,017
Deferred income taxes	33,131	32,959
Other noncurrent liabilities	10,694	10,819
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,204	1,066
Equity:
Common stock	29	30
Other shareholders' equity	51,687	52,681
Total Comcast Corporation shareholders' equity	51,716	52,711
Noncontrolling interests	249	357
Total equity	51,965	53,068	53,653	51,058
Total liabilities and equity	158,958	159,339
Comcast Parent [Member]
Assets
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	342	267
Total current assets	342	267
Film and television costs	0	0
Investments	30	36
Investments in and amounts due from subsidiaries eliminated upon consolidation	84,507	84,142
Property and equipment, net	204	199
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	11	11
Other noncurrent assets, net	1,248	1,224
Total assets	86,342	85,879
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	8	19
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	1,634	1,547
Current portion of long-term debt	750	1,650
Total current liabilities	2,392	3,216
Long-term debt, less current portion	29,829	27,616
Deferred income taxes	0	0
Other noncurrent liabilities	2,405	2,336
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Equity:
Common stock	29	30
Other shareholders' equity	51,687	52,681
Total Comcast Corporation shareholders' equity	51,716	52,711
Noncontrolling interests	0	0
Total equity	51,716	52,711
Total liabilities and equity	86,342	85,879
Comcast Holdings [Member]
Assets
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	109,269	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	149	148
Total assets	109,418	103,568
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	335	283
Current portion of long-term debt	0	0
Total current liabilities	335	283
Long-term debt, less current portion	133	126
Deferred income taxes	642	701
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Equity:
Common stock	0	0
Other shareholders' equity	108,308	102,458
Total Comcast Corporation shareholders' equity	108,308	102,458
Noncontrolling interests	0	0
Total equity	108,308	102,458
Total liabilities and equity	109,418	103,568
CCCL Parent [Member]
Assets
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	116,604	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	116,604	110,323
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	384	233
Current portion of long-term debt	0	0
Total current liabilities	384	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
Equity:
Common stock	0	0
Other shareholders' equity	114,392	108,263
Total Comcast Corporation shareholders' equity	114,392	108,263
Noncontrolling interests	0	0
Total equity	114,392	108,263
Total liabilities and equity	116,604	110,323
Combined CCHMO Parents [Member]
Assets
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	63,108	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	63,108	58,677
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	1
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	11	47
Current portion of long-term debt	0	677
Total current liabilities	11	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
Equity:
Common stock	0	0
Other shareholders' equity	62,275	57,130
Total Comcast Corporation shareholders' equity	62,275	57,130
Noncontrolling interests	0	0
Total equity	62,275	57,130
Total liabilities and equity	63,108	58,677
NBCUniversal Media Parent [Member]
Assets
Cash and cash equivalents	209	385	196	336
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	39	41
Total current assets	248	426
Film and television costs	0	0
Investments	508	378
Investments in and amounts due from subsidiaries eliminated upon consolidation	42,103	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	87	92
Total assets	42,946	42,135
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	431	331
Current portion of long-term debt	1,007	1,006
Total current liabilities	1,438	1,337
Long-term debt, less current portion	8,223	9,218
Deferred income taxes	59	67
Other noncurrent liabilities	1,121	1,143
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Equity:
Common stock	0	0
Other shareholders' equity	32,105	30,370
Total Comcast Corporation shareholders' equity	32,105	30,370
Noncontrolling interests	0	0
Total equity	32,105	30,370
Total liabilities and equity	42,946	42,135
Comcast Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	1,684	3,525	4,351	1,382
Investments [Current]	137	602
Receivables, net	6,527	6,321
Programming rights	1,130	839
Other current assets	1,433	1,551
Total current assets	10,911	12,838
Film and television costs	5,712	5,727
Investments	2,785	2,721
Investments in and amounts due from subsidiaries eliminated upon consolidation	107,420	98,152
Property and equipment, net	31,966	30,754
Franchise rights	59,364	59,364
Goodwill	27,492	27,316
Other intangible assets, net	16,885	16,969
Other noncurrent assets, net	2,137	1,949
Total assets	264,672	255,790
Liabilities and Equity
Accounts payable and accrued expenses related to trade creditors	5,988	5,618
Accrued participations and residuals	1,491	1,347
Accrued expenses and other current liabilities [condensed]	3,925	3,767
Current portion of long-term debt	1,395	884
Total current liabilities	12,799	11,616
Long-term debt, less current portion	3,770	4,408
Deferred income taxes	33,405	33,127
Other noncurrent liabilities	7,314	7,484
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,204	1,066
Equity:
Common stock	0	0
Other shareholders' equity	205,931	197,732
Total Comcast Corporation shareholders' equity	205,931	197,732
Noncontrolling interests	249	357
Total equity	206,180	198,089
Total liabilities and equity	264,672	255,790
Elimination and Consolidation Adjustments [Member]
Assets
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	(523,011)	(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	(1,121)	(1,080)
Total assets	(524,132)	(497,033)
Liabilities and Equity
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	(975)	(936)
Other noncurrent liabilities	(146)	(144)
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Equity:
Common stock	0	0
Other shareholders' equity	(523,011)	(495,953)
Total Comcast Corporation shareholders' equity	(523,011)	(495,953)
Noncontrolling interests	0	0
Total equity	(523,011)	(495,953)
Total liabilities and equity	$ (524,132)	$ (497,033)