Condensed Consolidating Financial Information (Condensed Consolidating Statement of Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Service revenue	$ 16,270	$ 15,211	$ 31,580	$ 30,089
Revenue	16,270	15,211	31,580	30,089
Programming and production	4,968	4,551	9,631	9,287
Other operating and administrative	4,570	4,365	9,036	8,610
Advertising, marketing and promotion	1,307	1,291	2,454	2,500
Depreciation	1,583	1,516	3,149	3,045
Amortization	407	409	808	810
Costs and expenses, total	12,835	12,132	25,078	24,252
Operating income (loss)	3,435	3,079	6,502	5,837
Interest expense	(636)	(625)	(1,289)	(1,265)
Investment income (loss), net	13	8	85	100
Equity in net income (losses) of investees, net	23	29	34	32
Other income (expense), net	(43)	(47)	30	(63)
Nonoperating income (Expense), Total	(643)	(635)	(1,140)	(1,196)
Income (loss) before income taxes	2,792	2,444	5,362	4,641
Income tax (expense) benefit	(1,048)	(811)	(1,973)	(1,561)
Net income (loss)	1,744	1,633	3,389	3,080
Net (income) loss attributable to noncontrolling interests	(10)	(285)	(218)	(508)
Net income (loss) attributable to Comcast Corporation	1,734	1,348	3,171	2,572
Comprehensive income attributable to Comcast Corporation	1,822	1,326	3,259	2,554
Comcast [Member]
Management fee revenue	225	210	443	414
Revenue	225	210	443	414
Other operating and administrative	101	99	199	191
Depreciation	8	8	15	15
Amortization	2	1	3	2
Costs and expenses, total	111	108	217	208
Operating income (loss)	114	102	226	206
Interest expense	(383)	(354)	(759)	(721)
Investment income (loss), net	1	2	2	3
Equity in net income (losses) of investees, net	1,910	1,511	3,518	2,905
Other income (expense), net	(1)		(2)
Nonoperating income (Expense), Total	1,527	1,159	2,759	2,187
Income (loss) before income taxes	1,641	1,261	2,985	2,393
Income tax (expense) benefit	93	87	186	179
Net income (loss)	1,734	1,348	3,171	2,572
Net income (loss) attributable to Comcast Corporation	1,734	1,348	3,171	2,572
Comprehensive income attributable to Comcast Corporation	1,822	1,326	3,259	2,554
Comcast Holdings [Member]
Interest expense	(2)	(8)	(5)	(16)
Investment income (loss), net	6	1	3	1
Equity in net income (losses) of investees, net	1,909	1,620	3,651	3,124
Other income (expense), net			0
Nonoperating income (Expense), Total	1,913	1,613	3,649	3,109
Income (loss) before income taxes	1,913	1,613	3,649	3,109
Income tax (expense) benefit	(1)	2	1	5
Net income (loss)	1,912	1,615	3,650	3,114
Net income (loss) attributable to Comcast Corporation	1,912	1,615	3,650	3,114
Comprehensive income attributable to Comcast Corporation	1,905	1,615	3,643	3,114
CCCL Parent [Member]
Management fee revenue	219	205	431	405
Revenue	219	205	431	405
Other operating and administrative	219	205	431	405
Costs and expenses, total	219	205	431	405
Interest expense	(46)	(83)	(124)	(165)
Equity in net income (losses) of investees, net	1,835	1,679	3,598	3,222
Other income (expense), net	2		2
Nonoperating income (Expense), Total	1,791	1,596	3,476	3,057
Income (loss) before income taxes	1,791	1,596	3,476	3,057
Income tax (expense) benefit	16	29	43	58
Net income (loss)	1,807	1,625	3,519	3,115
Net income (loss) attributable to Comcast Corporation	1,807	1,625	3,519	3,115
Comprehensive income attributable to Comcast Corporation	1,808	1,627	3,522	3,119
Combined CCHMO Parents [Member]
Management fee revenue	137	127	270	252
Revenue	137	127	270	252
Other operating and administrative	137	127	270	252
Costs and expenses, total	137	127	270	252
Interest expense	(33)	(33)	(66)	(69)
Equity in net income (losses) of investees, net	1,349	1,326	2,611	2,375
Nonoperating income (Expense), Total	1,316	1,293	2,545	2,306
Income (loss) before income taxes	1,316	1,293	2,545	2,306
Income tax (expense) benefit	12	11	23	24
Net income (loss)	1,328	1,304	2,568	2,330
Net income (loss) attributable to Comcast Corporation	1,328	1,304	2,568	2,330
Comprehensive income attributable to Comcast Corporation	1,328	1,304	2,568	2,330
NBCUniversal Media Parent [Member]
Revenue		0
Other operating and administrative	205	222	430	475
Costs and expenses, total	205	222	430	475
Operating income (loss)	(205)	(222)	(430)	(475)
Interest expense	(123)	(105)	(243)	(207)
Investment income (loss), net	5		1
Equity in net income (losses) of investees, net	951	841	1,660	1,584
Other income (expense), net		(12)		(13)
Nonoperating income (Expense), Total	833	724	1,418	1,364
Income (loss) before income taxes	628	502	988	889
Income tax (expense) benefit	(5)	11	(10)	9
Net income (loss)	623	513	978	898
Net income (loss) attributable to Comcast Corporation	623	513	978	898
Comprehensive income attributable to Comcast Corporation	599	495	932	881
Comcast Non-Guarantor Subsidiaries [Member]
Service revenue	16,270	15,211	31,580	30,089
Revenue	16,270	15,211	31,580	30,089
Programming and production	4,968	4,551	9,631	9,287
Other operating and administrative	4,489	4,254	8,850	8,358
Advertising, marketing and promotion	1,307	1,291	2,454	2,500
Depreciation	1,575	1,508	3,134	3,030
Amortization	405	408	805	808
Costs and expenses, total	12,744	12,012	24,874	23,983
Operating income (loss)	3,526	3,199	6,706	6,106
Interest expense	(49)	(42)	(92)	(87)
Investment income (loss), net	1	5	79	96
Equity in net income (losses) of investees, net	646	542	1,012	930
Other income (expense), net	(44)	(35)	30	(50)
Nonoperating income (Expense), Total	554	470	1,029	889
Income (loss) before income taxes	4,080	3,669	7,735	6,995
Income tax (expense) benefit	(1,163)	(951)	(2,216)	(1,836)
Net income (loss)	2,917	2,718	5,519	5,159
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock	(10)	(285)	(218)	(508)
Net income (loss) attributable to Comcast Corporation	2,907	2,433	5,301	4,651
Comprehensive income attributable to Comcast Corporation	3,007	2,447	5,414	4,663
Elimination and Consolidation Adjustments [Member]
Management fee revenue	(581)	(542)	(1,144)	(1,071)
Revenue	(581)	(542)	(1,144)	(1,071)
Other operating and administrative	(581)	(542)	(1,144)	(1,071)
Costs and expenses, total	(581)	(542)	(1,144)	(1,071)
Equity in net income (losses) of investees, net	(8,577)	(7,490)	(16,016)	(14,108)
Nonoperating income (Expense), Total	(8,577)	(7,490)	(16,016)	(14,108)
Income (loss) before income taxes	(8,577)	(7,490)	(16,016)	(14,108)
Net income (loss)	(8,577)	(7,490)	(16,016)	(14,108)
Net income (loss) attributable to Comcast Corporation	(8,577)	(7,490)	(16,016)	(14,108)
Comprehensive income attributable to Comcast Corporation	$ (8,647)	$ (7,488)	$ (16,079)	$ (14,107)