Condensed Consolidating Financial Information (Condensed Consolidating Statement of Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Service revenue	$ 14,878	$ 12,128
Management fee revenue	0	0
Revenue	14,878	12,128
Operating costs and expenses	10,190	8,062
Depreciation	1,529	1,486
Amortization	401	356
Costs and expenses, total	12,120	9,904
Operating income (loss)	2,758	2,224
Interest expense	(640)	(605)
Investment income (loss), net	92	89
Equity in net income (losses) of investees, net	3	(37)
Other income (expense), net	(16)	(36)
Nonoperating income (Expense), Total	(561)	(589)
Income (loss) before income taxes	2,197	1,635
Income tax (expense) benefit	(750)	(596)
Net income (loss)	1,447	1,039
Net (income) loss attributable to noncontrolling interests	(223)	(96)
Net income (loss) attributable to Comcast Corporation	1,224	943
Comprehensive income attributable to Comcast Corporation	1,228	945
Comcast [Member]
Service revenue	0	0
Management fee revenue	204	198
Revenue	204	198
Operating costs and expenses	92	148
Depreciation	7	7
Amortization	1	1
Costs and expenses, total	100	156
Operating income (loss)	104	42
Interest expense	(367)	(361)
Investment income (loss), net	1	1
Equity in net income (losses) of investees, net	1,394	1,161
Other income (expense), net	0	(17)
Nonoperating income (Expense), Total	1,028	784
Income (loss) before income taxes	1,132	826
Income tax (expense) benefit	92	117
Net income (loss)	1,224	943
Net (income) loss attributable to noncontrolling interests	0	0
Net income (loss) attributable to Comcast Corporation	1,224	943
Comprehensive income attributable to Comcast Corporation	1,227	941
CCCL Parent [Member]
Service revenue	0	0
Management fee revenue	200	185
Revenue	200	185
Operating costs and expenses	200	185
Depreciation	0	0
Amortization	0	0
Costs and expenses, total	200	185
Operating income (loss)	0	0
Interest expense	(82)	(91)
Investment income (loss), net	0	0
Equity in net income (losses) of investees, net	1,543	1,323
Other income (expense), net	0	0
Nonoperating income (Expense), Total	1,461	1,232
Income (loss) before income taxes	1,461	1,232
Income tax (expense) benefit	29	32
Net income (loss)	1,490	1,264
Net (income) loss attributable to noncontrolling interests	0	0
Net income (loss) attributable to Comcast Corporation	1,490	1,264
Comprehensive income attributable to Comcast Corporation	1,492	1,266
Combined CCHMO Parents [Member]
Service revenue	0	0
Management fee revenue	125	115
Revenue	125	115
Operating costs and expenses	125	115
Depreciation	0	0
Amortization	0	0
Costs and expenses, total	125	115
Operating income (loss)	0	0
Interest expense	(36)	(43)
Investment income (loss), net	0	0
Equity in net income (losses) of investees, net	1,049	794
Other income (expense), net	0	0
Nonoperating income (Expense), Total	1,013	751
Income (loss) before income taxes	1,013	751
Income tax (expense) benefit	13	15
Net income (loss)	1,026	766
Net (income) loss attributable to noncontrolling interests	0	0
Net income (loss) attributable to Comcast Corporation	1,026	766
Comprehensive income attributable to Comcast Corporation	1,026	766
Comcast Holdings [Member]
Service revenue	0	0
Management fee revenue	0	0
Revenue	0	0
Operating costs and expenses	0	5
Depreciation	0	0
Amortization	0	0
Costs and expenses, total	0	5
Operating income (loss)	0	(5)
Interest expense	(8)	(8)
Investment income (loss), net	0	4
Equity in net income (losses) of investees, net	1,504	1,292
Other income (expense), net	0	1
Nonoperating income (Expense), Total	1,496	1,289
Income (loss) before income taxes	1,496	1,284
Income tax (expense) benefit	3	3
Net income (loss)	1,499	1,287
Net (income) loss attributable to noncontrolling interests	0	0
Net income (loss) attributable to Comcast Corporation	1,499	1,287
Comprehensive income attributable to Comcast Corporation	1,499	1,287
Comcast Non-Guarantor Subsidiaries [Member]
Service revenue	14,878	12,128
Management fee revenue	0	0
Revenue	14,878	12,128
Operating costs and expenses	10,302	8,107
Depreciation	1,522	1,479
Amortization	400	355
Costs and expenses, total	12,224	9,941
Operating income (loss)	2,654	2,187
Interest expense	(147)	(102)
Investment income (loss), net	91	84
Equity in net income (losses) of investees, net	3	(37)
Other income (expense), net	(16)	(20)
Nonoperating income (Expense), Total	(69)	(75)
Income (loss) before income taxes	2,585	2,112
Income tax (expense) benefit	(887)	(763)
Net income (loss)	1,698	1,349
Net (income) loss attributable to noncontrolling interests	(223)	(96)
Net income (loss) attributable to Comcast Corporation	1,475	1,253
Comprehensive income attributable to Comcast Corporation	1,474	1,255
Elimination and Consolidation Adjustments [Member]
Service revenue	0	0
Management fee revenue	(529)	(498)
Revenue	(529)	(498)
Operating costs and expenses	(529)	(498)
Depreciation	0	0
Amortization	0	0
Costs and expenses, total	(529)	(498)
Operating income (loss)	0	0
Interest expense	0	0
Investment income (loss), net	0	0
Equity in net income (losses) of investees, net	(5,490)	(4,570)
Other income (expense), net	0	0
Nonoperating income (Expense), Total	(5,490)	(4,570)
Income (loss) before income taxes	(5,490)	(4,570)
Income tax (expense) benefit	0	0
Net income (loss)	(5,490)	(4,570)
Net (income) loss attributable to noncontrolling interests	0	0
Net income (loss) attributable to Comcast Corporation	(5,490)	(4,570)
Comprehensive income attributable to Comcast Corporation	$ (5,490)	$ (4,570)