Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities
Net cash provided by (used in) operating activities	$ 16,945,000,000	$ 14,160,000,000	$ 14,854,000,000
Investing Activities
Capital expenditures	(7,420,000,000)	(6,596,000,000)	(5,714,000,000)
Cash paid for intangible assets	(1,122,000,000)	(1,009,000,000)	(923,000,000)
Acquisitions and construction of real estate properties	(43,000,000)	(1,904,000,000)	0
Acquisitions, net of cash acquired	(477,000,000)	(99,000,000)	(90,000,000)
Proceeds from sales of businesses and investments	666,000,000	1,083,000,000	3,102,000,000
Return of capital from investees	25,000,000	149,000,000	2,362,000,000
Purchases of investments	(191,000,000)us-gaap_PaymentsToAcquireInvestments	(1,223,000,000)us-gaap_PaymentsToAcquireInvestments	(297,000,000)us-gaap_PaymentsToAcquireInvestments
Other	(171,000,000)	85,000,000	74,000,000
Net cash provided by (used in) investing activities	(8,733,000,000)	(9,514,000,000)	(1,486,000,000)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	(504,000,000)	1,345,000,000	(544,000,000)
Proceeds from borrowings	4,182,000,000us-gaap_ProceedsFromOtherDebt	2,933,000,000us-gaap_ProceedsFromOtherDebt	4,544,000,000us-gaap_ProceedsFromOtherDebt
Repurchases and repayments of debt	(3,175,000,000)us-gaap_RepaymentsOfOtherDebt	(2,444,000,000)us-gaap_RepaymentsOfOtherDebt	(2,881,000,000)us-gaap_RepaymentsOfOtherDebt
Repurchases and retirements of common stock	(4,251,000,000)	(2,000,000,000)	(3,000,000,000)
Dividends paid	(2,254,000,000)us-gaap_PaymentsOfDividends	(1,964,000,000)us-gaap_PaymentsOfDividends	(1,608,000,000)us-gaap_PaymentsOfDividends
Issuances of common stock	35,000,000	40,000,000	233,000,000
Purchase of NBCUniversal noncontrolling common equity interest	0	(10,761,000,000)	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	(220,000,000)	(215,000,000)	(691,000,000)
Settlement of Station Venture liability	0	(602,000,000)	0
Other	167,000,000	(211,000,000)	(90,000,000)
Net cash provided by (used in) financing activities	(6,020,000,000)	(13,879,000,000)	(4,037,000,000)
Increase (decrease) in cash and cash equivalents	2,192,000,000	(9,233,000,000)	9,331,000,000
Cash and cash equivalents, beginning of year	1,718,000,000	10,951,000,000	1,620,000,000
Cash and cash equivalents, end of year	3,910,000,000	1,718,000,000	10,951,000,000
Elimination and Consolidation Adjustments [Member]
Operating Activities
Net cash provided by (used in) operating activities	0	0	0
Investing Activities
Net transactions with affiliates	0	0	0
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Return of capital from investees	0	0	0
Purchases of investments	0	0	0
Other	0	0	0
Net cash provided by (used in) investing activities	0	0	0
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	0	0	0
Repurchases and retirements of common stock	0	0	0
Dividends paid	0	0	0
Issuances of common stock	0	0	0
Purchase of NBCUniversal noncontrolling common equity interest		0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Settlement of Station Venture liability		0
Other	0	0	0
Net cash provided by (used in) financing activities	0	0	0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Comcast Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities	(354,000,000)	(600,000,000)	(362,000,000)
Investing Activities
Net transactions with affiliates	4,784,000,000	66,000,000	3,845,000,000
Capital expenditures	(3,000,000)	(7,000,000)	(10,000,000)
Cash paid for intangible assets	(6,000,000)	(4,000,000)	(6,000,000)
Acquisitions and construction of real estate properties	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Return of capital from investees	0	0	0
Purchases of investments	(19,000,000)	(11,000,000)	0
Other	0	0	0
Net cash provided by (used in) investing activities	4,756,000,000	44,000,000	3,829,000,000
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	(1,350,000,000)	1,349,000,000	(1,000,000)
Proceeds from borrowings	4,180,000,000	2,933,000,000	2,536,000,000
Repurchases and repayments of debt	(1,000,000,000)	0	(1,726,000,000)
Repurchases and retirements of common stock	(4,251,000,000)	(2,000,000,000)	(3,000,000,000)
Dividends paid	(2,254,000,000)	(1,964,000,000)	(1,608,000,000)
Issuances of common stock	35,000,000	40,000,000	233,000,000
Purchase of NBCUniversal noncontrolling common equity interest		0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Settlement of Station Venture liability		0
Other	238,000,000	198,000,000	99,000,000
Net cash provided by (used in) financing activities	(4,402,000,000)	556,000,000	(3,467,000,000)
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Comcast Holdings [Member]
Operating Activities
Net cash provided by (used in) operating activities	9,000,000	(3,000,000)	(7,000,000)
Investing Activities
Net transactions with affiliates	(9,000,000)	3,000,000	206,000,000
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Return of capital from investees	0	0	0
Purchases of investments	0	0	0
Other	0	0	3,000,000
Net cash provided by (used in) investing activities	(9,000,000)	3,000,000	209,000,000
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	0	0	(202,000,000)
Repurchases and retirements of common stock	0	0	0
Dividends paid	0	0	0
Issuances of common stock	0	0	0
Purchase of NBCUniversal noncontrolling common equity interest		0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Settlement of Station Venture liability		0
Other	0	0	0
Net cash provided by (used in) financing activities	0	0	(202,000,000)
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
CCCL Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities	(57,000,000)	(151,000,000)	(177,000,000)
Investing Activities
Net transactions with affiliates	57,000,000	2,248,000,000	177,000,000
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Return of capital from investees	0	0	0
Purchases of investments	0	0	0
Other	0	0	0
Net cash provided by (used in) investing activities	57,000,000	2,248,000,000	177,000,000
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	0	(2,097,000,000)	0
Repurchases and retirements of common stock	0	0	0
Dividends paid	0	0	0
Issuances of common stock	0	0	0
Purchase of NBCUniversal noncontrolling common equity interest		0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Settlement of Station Venture liability		0
Other	0	0	0
Net cash provided by (used in) financing activities	0	(2,097,000,000)	0
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Combined CCHMO Parents [Member]
Operating Activities
Net cash provided by (used in) operating activities	(82,000,000)	(94,000,000)	(114,000,000)
Investing Activities
Net transactions with affiliates	82,000,000	332,000,000	667,000,000
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	0	0	0
Return of capital from investees	0	0	0
Purchases of investments	0	0	0
Other	0	0	0
Net cash provided by (used in) investing activities	82,000,000	332,000,000	667,000,000
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	0
Proceeds from borrowings	0	0	0
Repurchases and repayments of debt	0	(238,000,000)	(553,000,000)
Repurchases and retirements of common stock	0	0	0
Dividends paid	0	0	0
Issuances of common stock	0	0	0
Purchase of NBCUniversal noncontrolling common equity interest		0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Settlement of Station Venture liability		0
Other	0	0	0
Net cash provided by (used in) financing activities	0	(238,000,000)	(553,000,000)
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
NBCUniversal Media Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities	(1,299,000,000)	(1,102,000,000)	(1,347,000,000)
Investing Activities
Net transactions with affiliates	2,247,000,000	(470,000,000)	4,850,000,000
Capital expenditures	0	0	0
Cash paid for intangible assets	0	0	0
Acquisitions and construction of real estate properties	0	0
Acquisitions, net of cash acquired	0	0	0
Proceeds from sales of businesses and investments	8,000,000	2,000,000	0
Return of capital from investees	1,000,000	128,000,000	0
Purchases of investments	(10,000,000)	(3,000,000)	(19,000,000)
Other	4,000,000	(20,000,000)	(22,000,000)
Net cash provided by (used in) investing activities	2,250,000,000	(363,000,000)	4,809,000,000
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	0	0	(550,000,000)
Proceeds from borrowings	0	0	1,995,000,000
Repurchases and repayments of debt	(902,000,000)	(88,000,000)	(2,000,000)
Repurchases and retirements of common stock	0	0	0
Dividends paid	0	0	0
Issuances of common stock	0	0	0
Purchase of NBCUniversal noncontrolling common equity interest		(3,200,000,000)
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	0	0	0
Settlement of Station Venture liability		0
Other	0	(40,000,000)	(14,000,000)
Net cash provided by (used in) financing activities	(902,000,000)	(3,328,000,000)	1,429,000,000
Increase (decrease) in cash and cash equivalents	49,000,000	(4,793,000,000)	4,891,000,000
Cash and cash equivalents, beginning of year	336,000,000	5,129,000,000	238,000,000
Cash and cash equivalents, end of year	385,000,000	336,000,000	5,129,000,000
Comcast Non-Guarantor Subsidiaries [Member]
Operating Activities
Net cash provided by (used in) operating activities	18,728,000,000	16,110,000,000	16,861,000,000
Investing Activities
Net transactions with affiliates	(7,161,000,000)	(2,179,000,000)	(9,745,000,000)
Capital expenditures	(7,417,000,000)	(6,589,000,000)	(5,704,000,000)
Cash paid for intangible assets	(1,116,000,000)	(1,005,000,000)	(917,000,000)
Acquisitions and construction of real estate properties	(43,000,000)	(1,904,000,000)
Acquisitions, net of cash acquired	(477,000,000)	(99,000,000)	(90,000,000)
Proceeds from sales of businesses and investments	658,000,000	1,081,000,000	3,102,000,000
Return of capital from investees	24,000,000	21,000,000	2,362,000,000
Purchases of investments	(162,000,000)	(1,209,000,000)	(278,000,000)
Other	(175,000,000)	105,000,000	93,000,000
Net cash provided by (used in) investing activities	(15,869,000,000)	(11,778,000,000)	(11,177,000,000)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net	846,000,000	(4,000,000)	7,000,000
Proceeds from borrowings	2,000,000	0	13,000,000
Repurchases and repayments of debt	(1,273,000,000)	(21,000,000)	(398,000,000)
Repurchases and retirements of common stock	0	0	0
Dividends paid	0	0	0
Issuances of common stock	0	0	0
Purchase of NBCUniversal noncontrolling common equity interest		(7,561,000,000)
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock	(220,000,000)	(215,000,000)	(691,000,000)
Settlement of Station Venture liability		(602,000,000)
Other	(71,000,000)	(369,000,000)	(175,000,000)
Net cash provided by (used in) financing activities	(716,000,000)	(8,772,000,000)	(1,244,000,000)
Increase (decrease) in cash and cash equivalents	2,143,000,000	(4,440,000,000)	4,440,000,000
Cash and cash equivalents, beginning of year	1,382,000,000	5,822,000,000	1,382,000,000
Cash and cash equivalents, end of year	$ 3,525,000,000	$ 1,382,000,000	$ 5,822,000,000

Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders and dividends for redeemable subsidiary preferred stock.

No definition available.