Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Cash and cash equivalents	$ 2,207	$ 1,620	$ 1,822	$ 5,984
Receivables, net	4,379	4,351
Programming rights	1,011	987
Other current assets	1,758	1,615
Total current assets	9,355	8,573
Film and television costs	5,112	5,227
Investments	10,149	9,854
Investments in and amounts due from subsidiaries eliminated upon consolidation	0	0
Property and equipment, net	26,962	27,559
Franchise rights	59,364	59,376
Goodwill	26,803	26,874
Other intangible assets, net	18,001	18,165
Other noncurrent assets, net	2,203	2,190
Total assets	157,949	157,818
Accounts payable and accrued expenses related to trade creditors	5,763	5,705
Accrued participations and residuals	1,394	1,255
Accrued expenses and other current liabilities	5,770	4,914
Current portion of long-term debt	2,705	1,367
Total current liabilities	15,632	13,241
Long-term debt, less current portion	35,080	37,942
Deferred income taxes	29,812	29,932
Other noncurrent liabilities	13,446	13,034
Redeemable noncontrolling interests	16,158	16,014
Common stock	31	32
Other shareholders' equity	47,445	47,242
Total Comcast Corporation shareholders' equity	47,476	47,274
Noncontrolling interests	345	381
Total equity	47,821	47,655	46,607	44,434
Total liabilities and equity	157,949	157,818
Comcast [Member]
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	169	235
Total current assets	169	235
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	71,062	71,222
Property and equipment, net	255	262
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	9	9
Other noncurrent assets, net	882	912
Total assets	72,377	72,640
Accounts payable and accrued expenses related to trade creditors	11	10
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	1,132	1,030
Current portion of long-term debt	589	26
Total current liabilities	1,732	1,066
Long-term debt, less current portion	21,345	22,451
Deferred income taxes	0	0
Other noncurrent liabilities	1,824	1,849
Redeemable noncontrolling interests	0	0
Common stock	31	32
Other shareholders' equity	47,445	47,242
Total Comcast Corporation shareholders' equity	47,476	47,274
Noncontrolling interests	0	0
Total equity	47,476	47,274
Total liabilities and equity	72,377	72,640
CCCL Parent [Member]
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	20	8
Total current assets	20	8
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	94,024	89,568
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	10	30
Total assets	94,054	89,606
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	287	189
Current portion of long-term debt	1,733	0
Total current liabilities	2,020	189
Long-term debt, less current portion	2,216	3,953
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Common stock	0	0
Other shareholders' equity	89,818	85,464
Total Comcast Corporation shareholders' equity	89,818	85,464
Noncontrolling interests	0	0
Total equity	89,818	85,464
Total liabilities and equity	94,054	89,606
Combined CCHMO Parents [Member]
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	1	3
Total current assets	1	3
Film and television costs	0	0
Investments	0	0
Investments in and amounts due from subsidiaries eliminated upon consolidation	47,950	45,725
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	5	5
Total assets	47,956	45,733
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	24	77
Current portion of long-term debt	0	554
Total current liabilities	24	631
Long-term debt, less current portion	1,762	1,764
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Common stock	0	0
Other shareholders' equity	46,170	43,338
Total Comcast Corporation shareholders' equity	46,170	43,338
Noncontrolling interests	0	0
Total equity	46,170	43,338
Total liabilities and equity	47,956	45,733
Comcast Holdings [Member]
Cash and cash equivalents	0	0	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	85,926	88,336
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	86,074	88,484
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	267	272
Current portion of long-term debt	202	202
Total current liabilities	469	474
Long-term debt, less current portion	112	111
Deferred income taxes	734	727
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests	0	0
Common stock	0	0
Other shareholders' equity	84,759	87,172
Total Comcast Corporation shareholders' equity	84,759	87,172
Noncontrolling interests	0	0
Total equity	84,759	87,172
Total liabilities and equity	86,074	88,484
Comcast Non-Guarantor Subsidiaries [Member]
Cash and cash equivalents	2,207	1,620	1,822	5,984
Receivables, net	4,379	4,351
Programming rights	1,011	987
Other current assets	1,568	1,369
Total current assets	9,165	8,327
Film and television costs	5,112	5,227
Investments	10,149	9,854
Investments in and amounts due from subsidiaries eliminated upon consolidation	40,567	36,949
Property and equipment, net	26,707	27,297
Franchise rights	59,364	59,376
Goodwill	26,803	26,874
Other intangible assets, net	17,992	18,156
Other noncurrent assets, net	1,818	1,761
Total assets	197,677	193,821
Accounts payable and accrued expenses related to trade creditors	5,752	5,695
Accrued participations and residuals	1,394	1,255
Accrued expenses and other current liabilities	4,060	3,346
Current portion of long-term debt	181	585
Total current liabilities	11,387	10,881
Long-term debt, less current portion	9,645	9,663
Deferred income taxes	29,595	29,728
Other noncurrent liabilities	11,765	11,328
Redeemable noncontrolling interests	16,158	16,014
Common stock	0	0
Other shareholders' equity	118,782	115,826
Total Comcast Corporation shareholders' equity	118,782	115,826
Noncontrolling interests	345	381
Total equity	119,127	116,207
Total liabilities and equity	197,677	193,821
Elimination and Consolidation Adjustments [Member]
Cash and cash equivalents	0	0	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	(339,529)	(331,800)
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	(660)	(666)
Total assets	(340,189)	(332,466)
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities	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	(517)	(523)
Other noncurrent liabilities	(143)	(143)
Redeemable noncontrolling interests	0	0
Common stock	0	0
Other shareholders' equity	(339,529)	(331,800)
Total Comcast Corporation shareholders' equity	(339,529)	(331,800)
Noncontrolling interests	0	0
Total equity	(339,529)	(331,800)
Total liabilities and equity	$ (340,189)	$ (332,466)