Comcast (CMCSA) 10-K 27 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Jun. 30, 2014
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	cmcsa
Entity Registrant Name	COMCAST CORP
Entity Central Index Key	1166691
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
NBCUniversal Media, LLC [Member]
Entity Registrant Name	NBCUniversal Media, LLC
Entity Central Index Key	902739
Entity Filer Category	Non-accelerated Filer
Entity Public Float		$0
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Class A Common Stock [Member]
Entity Common Stock, Shares Outstanding	2,131,137,862
Entity Public Float		115,221
Class A Special Common Stock [Member]
Entity Common Stock, Shares Outstanding	400,484,837
Entity Public Float		$22,369
Class B Common Stock [Member]
Entity Common Stock, Shares Outstanding	9,444,375

Consolidated_Balance_Sheet

Consolidated Balance Sheet (USD $)	Dec. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$3,910,000,000	$1,718,000,000
Investments [Current]	602,000,000	3,573,000,000
Receivables, net	6,321,000,000	6,376,000,000
Programming rights	839,000,000	928,000,000
Other current assets	1,859,000,000	1,480,000,000
Total current assets	13,531,000,000	14,075,000,000
Film and television costs	5,727,000,000	4,994,000,000
Investments	3,135,000,000	3,770,000,000
Property and equipment, net	30,953,000,000	29,840,000,000
Franchise rights	59,364,000,000	59,364,000,000
Goodwill	27,316,000,000	27,098,000,000
Other intangible assets, net	16,980,000,000	17,329,000,000
Other noncurrent assets, net	2,333,000,000	2,343,000,000
Total assets	159,339,000,000	158,813,000,000
Current Liabilities:
Accounts payable and accrued expenses related to trade creditors	5,638,000,000	5,528,000,000
Accrued participations and residuals	1,347,000,000	1,239,000,000
Deferred revenue	915,000,000	898,000,000
Accrued expenses and other current liabilities	5,293,000,000	7,967,000,000
Current portion of long-term debt	4,217,000,000	3,280,000,000
Total current liabilities	17,410,000,000	18,912,000,000
Long-term debt, less current portion	44,017,000,000	44,567,000,000
Deferred income taxes	32,959,000,000	31,935,000,000
Other noncurrent liabilities	10,819,000,000	11,384,000,000
Commitments and contingencies
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,066,000,000	957,000,000
Equity:
Preferred stock - authorized, 20,000,000 shares; issued, zero	0	0
Common stock	30,000,000	30,000,000
Additional paid-in capital	38,805,000,000	38,890,000,000
Retained earnings	21,539,000,000	19,235,000,000
Treasury stock, 365,460,750 Class A common shares and 70,934,764 Class A Special common shares	-7,517,000,000	-7,517,000,000
Accumulated other comprehensive income (loss)	-146,000,000	56,000,000
Total Comcast Corporation shareholders' equity	52,711,000,000	50,694,000,000
Noncontrolling interests	357,000,000	364,000,000
Total equity	53,068,000,000	51,058,000,000
Total liabilities and equity	159,339,000,000	158,813,000,000
NBCUniversal Media, LLC [Member]
Current Assets:
Cash and cash equivalents	1,248,000,000	967,000,000
Receivables, net	4,842,000,000	4,911,000,000
Programming rights	825,000,000	903,000,000
Other current assets	823,000,000	615,000,000
Total current assets	7,738,000,000	7,396,000,000
Film and television costs	5,714,000,000	4,983,000,000
Investments	882,000,000	884,000,000
Property and equipment, net	8,138,000,000	7,650,000,000
Goodwill	14,908,000,000	14,882,000,000
Intangible assets, net	14,187,000,000	14,857,000,000
Other noncurrent assets, net	1,050,000,000	1,087,000,000
Total assets	52,617,000,000	51,739,000,000
Current Liabilities:
Accounts payable and accrued expenses related to trade creditors	1,388,000,000	1,583,000,000
Accrued participations and residuals	1,347,000,000	1,239,000,000
Program obligations	687,000,000	657,000,000
Deferred revenue	821,000,000	846,000,000
Accrued expenses and other current liabilities	1,422,000,000	1,465,000,000
Note payable to Comcast	865,000,000	799,000,000
Current portion of long-term debt	1,023,000,000	906,000,000
Total current liabilities	7,553,000,000	7,495,000,000
Long-term debt, less current portion	9,226,000,000	10,259,000,000
Accrued participations residuals and program obligations	1,149,000,000	1,015,000,000
Other noncurrent liabilities	3,722,000,000	3,412,000,000
Commitments and contingencies
Redeemable noncontrolling interests	330,000,000	231,000,000
Equity:
Member's capital	30,529,000,000	29,056,000,000
Accumulated other comprehensive income (loss)	-159,000,000	-16,000,000
Total NBCUniversal member's equity	30,370,000,000	29,040,000,000
Noncontrolling interests	267,000,000	287,000,000
Total equity	30,637,000,000	29,327,000,000
Total liabilities and equity	52,617,000,000	51,739,000,000
Class A Common Stock [Member]
Equity:
Common stock	25,000,000	25,000,000
Class B Common Stock [Member]
Equity:
Common stock	0	0
Class A Special Common Stock [Member]
Equity:
Common stock	$5,000,000	$5,000,000

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Preferred stock, authorized	20,000,000	20,000,000
Preferred stock, issued	0	0
Class A Common Stock [Member]
Common stock, par value	$0.01	$0.01
Common stock, authorized	7,500,000,000	7,500,000,000
Common stock, issued	2,496,598,612	2,503,535,883
Common stock, outstanding	2,131,137,862	2,138,075,133
Treasury stock common shares	365,460,750	365,460,750
Class A Special Common Stock [Member]
Common stock, par value	$0.01	$0.01
Common stock, authorized	7,500,000,000	7,500,000,000
Common stock, issued	471,419,601	529,964,944
Common stock, outstanding	400,484,837	459,030,180
Treasury stock common shares	70,934,764	70,934,764
Class B Common Stock [Member]
Common stock, par value	$0.01	$0.01
Common stock, authorized	75,000,000	75,000,000
Common stock, issued	9,444,375	9,444,375
Common stock, outstanding	9,444,375	9,444,375

Consolidated_Statement_of_Inco

Consolidated Statement of Income (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$17,732,000,000	$16,791,000,000	$16,844,000,000	$17,408,000,000	$16,926,000,000	$16,151,000,000	$16,270,000,000	$15,310,000,000	$68,775,000,000	$64,657,000,000	$62,570,000,000
Costs and Expenses:
Programming and production									20,912,000,000	19,670,000,000	19,929,000,000
Other operating and administrative									19,862,000,000	18,584,000,000	17,833,000,000
Advertising, marketing and promotion									5,078,000,000	4,969,000,000	4,831,000,000
Depreciation									6,337,000,000	6,254,000,000	6,150,000,000
Amortization									1,682,000,000	1,617,000,000	1,648,000,000
Total costs and expenses									53,871,000,000	51,094,000,000	50,391,000,000
Operating income	3,787,000,000	3,745,000,000	3,804,000,000	3,568,000,000	3,647,000,000	3,414,000,000	3,435,000,000	3,067,000,000	14,904,000,000	13,563,000,000	12,179,000,000
Other Income (Expense):
Interest expense									-2,617,000,000	-2,574,000,000	-2,521,000,000
Investment income (loss), net									296,000,000	576,000,000	219,000,000
Equity in net income (losses) of investees, net									97,000,000	-86,000,000	959,000,000
Other income (expense), net									-215,000,000	-364,000,000	773,000,000
Nonoperating income (expense)									-2,439,000,000	-2,448,000,000	-570,000,000
Income before income taxes									12,465,000,000	11,115,000,000	11,609,000,000
Income tax expense									-3,873,000,000	-3,980,000,000	-3,744,000,000
Net income									8,592,000,000	7,135,000,000	7,865,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									-212,000,000	-319,000,000	-1,662,000,000
Net income attributable to Parent	1,925,000,000	2,592,000,000	1,992,000,000	1,871,000,000	1,913,000,000	1,732,000,000	1,734,000,000	1,437,000,000	8,380,000,000	6,816,000,000	6,203,000,000
Basic earnings per common share attributable to Comcast Corporation shareholders	$0.75	$1	$0.77	$0.72	$0.73	$0.66	$0.66	$0.55	$3.24	$2.60	$2.32
Diluted earnings per common share attributable to Comcast Corporation shareholders	$0.74	$0.99	$0.76	$0.71	$0.72	$0.65	$0.65	$0.54	$3.20	$2.56	$2.28
Dividends declared per common share	$0.23	$0.23	$0.23	$0.23	$0.20	$0.20	$0.20	$0.20	$0.90	$0.78	$0.65
NBCUniversal Media, LLC [Member]
Revenue									25,428,000,000	23,650,000,000	23,812,000,000
Costs and Expenses:
Programming and production									12,318,000,000	11,770,000,000	12,710,000,000
Other operating and administrative									5,364,000,000	4,949,000,000	4,763,000,000
Advertising, marketing and promotion									2,158,000,000	2,199,000,000	2,232,000,000
Depreciation									654,000,000	639,000,000	562,000,000
Amortization									841,000,000	772,000,000	764,000,000
Total costs and expenses									21,335,000,000	20,329,000,000	21,031,000,000
Operating income									4,093,000,000	3,321,000,000	2,781,000,000
Other Income (Expense):
Interest expense									-508,000,000	-515,000,000	-480,000,000
Investment income (loss), net									27,000,000	17,000,000	27,000,000
Equity in net income (losses) of investees, net									46,000,000	-93,000,000	183,000,000
Other income (expense), net									-218,000,000	-402,000,000	917,000,000
Nonoperating income (expense)									-653,000,000	-993,000,000	647,000,000
Income before income taxes									3,440,000,000	2,328,000,000	3,428,000,000
Income tax expense									-143,000,000	-206,000,000	-197,000,000
Net income									3,297,000,000	2,122,000,000	3,231,000,000
Net income attributable to Parent									$3,115,000,000	$1,968,000,000	$3,055,000,000

Consolidated_Statement_of_Inco1

Consolidated Statement of Income (NBCUniversal) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$17,732,000,000	$16,791,000,000	$16,844,000,000	$17,408,000,000	$16,926,000,000	$16,151,000,000	$16,270,000,000	$15,310,000,000	$68,775,000,000	$64,657,000,000	$62,570,000,000
Costs and Expenses:
Programming and production									20,912,000,000	19,670,000,000	19,929,000,000
Other operating and administrative									19,862,000,000	18,584,000,000	17,833,000,000
Advertising, marketing and promotion									5,078,000,000	4,969,000,000	4,831,000,000
Depreciation									6,337,000,000	6,254,000,000	6,150,000,000
Amortization									1,682,000,000	1,617,000,000	1,648,000,000
Total costs and expenses									53,871,000,000	51,094,000,000	50,391,000,000
Operating income	3,787,000,000	3,745,000,000	3,804,000,000	3,568,000,000	3,647,000,000	3,414,000,000	3,435,000,000	3,067,000,000	14,904,000,000	13,563,000,000	12,179,000,000
Other Income (Expense):
Interest expense									-2,617,000,000	-2,574,000,000	-2,521,000,000
Investment income (loss), net									296,000,000	576,000,000	219,000,000
Equity in net income (losses) of investees, net									97,000,000	-86,000,000	959,000,000
Other income (expense), net									-215,000,000	-364,000,000	773,000,000
Nonoperating income (expense)									-2,439,000,000	-2,448,000,000	-570,000,000
Income before income taxes									12,465,000,000	11,115,000,000	11,609,000,000
Income tax expense									-3,873,000,000	-3,980,000,000	-3,744,000,000
Net income									8,592,000,000	7,135,000,000	7,865,000,000
Net income attributable to Parent	1,925,000,000	2,592,000,000	1,992,000,000	1,871,000,000	1,913,000,000	1,732,000,000	1,734,000,000	1,437,000,000	8,380,000,000	6,816,000,000	6,203,000,000
N B C Universal Media L L C [Member]
Revenue									25,428,000,000	23,650,000,000	23,812,000,000
Costs and Expenses:
Programming and production									12,318,000,000	11,770,000,000	12,710,000,000
Other operating and administrative									5,364,000,000	4,949,000,000	4,763,000,000
Advertising, marketing and promotion									2,158,000,000	2,199,000,000	2,232,000,000
Depreciation									654,000,000	639,000,000	562,000,000
Amortization									841,000,000	772,000,000	764,000,000
Total costs and expenses									21,335,000,000	20,329,000,000	21,031,000,000
Operating income									4,093,000,000	3,321,000,000	2,781,000,000
Other Income (Expense):
Interest expense									-508,000,000	-515,000,000	-480,000,000
Investment income (loss), net									27,000,000	17,000,000	27,000,000
Equity in net income (losses) of investees, net									46,000,000	-93,000,000	183,000,000
Other income (expense), net									-218,000,000	-402,000,000	917,000,000
Nonoperating income (expense)									-653,000,000	-993,000,000	647,000,000
Income before income taxes									3,440,000,000	2,328,000,000	3,428,000,000
Income tax expense									-143,000,000	-206,000,000	-197,000,000
Net income									3,297,000,000	2,122,000,000	3,231,000,000
Net (income) loss attributable to noncontrolling interests									-182,000,000	-154,000,000	-176,000,000
Net income attributable to Parent									$3,115,000,000	$1,968,000,000	$3,055,000,000

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Income (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income	$8,592	$7,135	$7,865
Unrealized gains (losses) on marketable securities, net of deferred taxes	33	185	161
Deferred gains (losses) on cash flow hedges, net of deferred taxes	-5	25	58
Amounts Reclassified To Net Income:
Realized (gains) losses on marketable securities, net of deferred taxes	-99	-301	0
Realized (gains) losses on cash flow hedges, net of deferred taxes	46	-3	-15
Employee benefit obligations, net of deferred taxes	-139	181	-31
Currency translation adjustments, net of deferred taxes	-38	-29	0
Comprehensive income	8,390	7,193	8,038
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock	-212	-319	-1,662
Other comprehensive (income) loss attributable to noncontrolling interests	0	9	-6
Comprehensive income attributable to Parent	8,178	6,883	6,370
NBCUniversal Media, LLC [Member]
Net income	3,297	2,122	3,231
Unrealized gains (losses) on marketable securities, net of deferred taxes	0	0	0
Deferred gains (losses) on cash flow hedges, net of deferred taxes	25	-5	0
Amounts Reclassified To Net Income:
Employee benefit obligations, net of deferred taxes	-106	95	14
Currency translation adjustments, net of deferred taxes	-62	-41	-1
Comprehensive income	3,154	2,171	3,244
Net (income) loss attributable to noncontrolling interests	-182	-154	-176
Comprehensive income attributable to Parent	$2,972	$2,017	$3,068

Consolidated_Statement_of_Comp1

Consolidated Statement of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Unrealized gains (losses) on marketable securities, deferred taxes	($19)	($110)	($95)
Deferred gains (losses) on cash flow hedges, deferred taxes	3	-14	-34
Realized (gains) losses on marketable securities, deferred taxes	59	177	0
Realized (gains) losses on cash flow hedges, deferred taxes	-27	2	8
Employee benefit obligations, deferred taxes	82	-108	22
Currency translation adjustments, deferred taxes	$23	$12	$0

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities
Net income	$8,592,000,000	$7,135,000,000	$7,865,000,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,019,000,000	7,871,000,000	7,798,000,000
Share-based compensation	513,000,000	419,000,000	371,000,000
Noncash interest expense (income), net	180,000,000	167,000,000	193,000,000
Equity in net (income) losses of investees, net	-97,000,000	86,000,000	-959,000,000
Cash received from investees	104,000,000	120,000,000	195,000,000
Net (gain) loss on investment activity and other	4,000,000	-169,000,000	-1,062,000,000
Deferred income taxes	1,165,000,000	16,000,000	139,000,000
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net	-33,000,000	-721,000,000	-823,000,000
Film and television costs, net	-562,000,000	44,000,000	22,000,000
Accounts payable and accrued expenses related to trade creditors	153,000,000	-667,000,000	366,000,000
Other operating assets and liabilities	-1,093,000,000	-141,000,000	749,000,000
Net cash provided by 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	-1,223,000,000	-297,000,000
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	4,182,000,000	2,933,000,000	4,544,000,000
Repurchases and repayments of debt	-3,175,000,000	-2,444,000,000	-2,881,000,000
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	-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
NBCUniversal Media, LLC [Member]
Operating Activities
Net income	3,297,000,000	2,122,000,000	3,231,000,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,495,000,000	1,411,000,000	1,326,000,000
Share-based compensation	0	7,000,000	7,000,000
Equity in net (income) losses of investees, net	-46,000,000	93,000,000	-183,000,000
Cash received from investees	74,000,000	90,000,000	189,000,000
Net (gain) loss on investment activity and other	136,000,000	345,000,000	-1,093,000,000
Deferred income taxes	-12,000,000	-10,000,000	15,000,000
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Current and noncurrent receivables, net	-25,000,000	-752,000,000	-643,000,000
Film and television costs, net	-571,000,000	2,000,000	100,000,000
Accounts payable and accrued expenses related to trade creditors	-88,000,000	-789,000,000	51,000,000
Other operating assets and liabilities	264,000,000	505,000,000	333,000,000
Net cash provided by operating activities	4,524,000,000	3,024,000,000	3,333,000,000
Investing Activities
Capital expenditures	-1,221,000,000	-1,160,000,000	-763,000,000
Cash paid for intangible assets	-130,000,000	-113,000,000	-113,000,000
Acquisitions of real estate properties	0	-1,705,000,000	0
Acquisitions, net of cash acquired	-118,000,000	-111,000,000	-90,000,000
Proceeds from sales of businesses and investments	13,000,000	2,000,000	3,026,000,000
Return of capital from investees	24,000,000	131,000,000	75,000,000
Purchases of investments	-35,000,000	-236,000,000	-117,000,000
Other	-146,000,000	-20,000,000	-9,000,000
Net cash provided by (used in) investing activities	-1,613,000,000	-3,212,000,000	2,009,000,000
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	-906,000,000	-92,000,000	-413,000,000
Proceeds from (repayments of) borrowings from Comcast, net	97,000,000	799,000,000	0
Redemption transaction distribution	0	-3,200,000,000	0
Distributions to member	-1,641,000,000	-1,422,000,000	-964,000,000
Distributions to noncontrolling interests	-177,000,000	-183,000,000	-216,000,000
Settlement of Station Venture liability	0	-602,000,000	0
Other	-3,000,000	-66,000,000	-81,000,000
Net cash provided by (used in) financing activities	-2,630,000,000	-4,766,000,000	-229,000,000
Increase (decrease) in cash and cash equivalents	281,000,000	-4,954,000,000	5,113,000,000
Cash and cash equivalents, beginning of year	967,000,000	5,921,000,000	808,000,000
Cash and cash equivalents, end of year	$1,248,000,000	$967,000,000	$5,921,000,000

Consolidated_Statement_of_Chan

Consolidated Statement of Changes in Equity (USD $)	Total	NBCUniversal Media, LLC [Member]	Redeemable Noncontrolling Interests And Redeemable Subisdiary Preferred Stock [Member]	Class A Common Stock [Member]	Class A Special Common Stock [Member]	Class B Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interest [Member]	Member's Capital [Member]
In Millions											NBCUniversal Media, LLC [Member]		NBCUniversal Media, LLC [Member]	NBCUniversal Media, LLC [Member]	NBCUniversal Media, LLC [Member]
Beginning balance at Dec. 31, 2011		$30,081									($78)		$361	$184	$29,798
Beginning Balance at Dec. 31, 2011	47,655		16,014	25	7	0	40,940	13,971	-7,517	-152		381
Stock compensation plans	372						612	-240
Repurchases and retirements of common stock	-3,000				-1		-1,081	-1,918
Employee stock purchase plans	80						80
Compensation Plans		7													7
Other comprehensive income (loss)	167	13	6							167	13
Redemption transaction distribution		0
Dividends declared	-1,736	-964						-1,736							-964
Purchase of subsidiary shares from noncontrolling interests														-47
Contributions from and (distributions to) noncontrolling interests, net	-169	-184	-493									-169	-184	-24
Other	76	88	-43				-4					80	84		4
Net income (loss)	6,351	3,213	1,514					6,203				148	158	18	3,055
Ending Balance at Dec. 31, 2012	49,796		16,998	25	6	0	40,547	16,280	-7,517	15		440
Ending balance at Dec. 31, 2012		32,254									-65		419	131	31,900
Stock compensation plans	232						603	-371
Repurchases and retirements of common stock	-2,000				-1		-555	-1,444
Employee stock purchase plans	98						98
Compensation Plans		7													7
Other comprehensive income (loss)	67	49	-9							67	49
Redemption transaction distribution		-3,200													-3,200
Dividends declared	-2,046	-1,422						-2,046							-1,422
Purchase of NBCUniversal noncontrolling common equity interest	-1,677		-17,006				-1,651			-26
Purchase of subsidiary shares from noncontrolling interests		-33													-33
Redeemable subsidiary preferred stock			725
Contributions from and (distributions to) noncontrolling interests, net	-136	-155	-22									-136	-155	-22
Other	-210	-275	70				-152					-58	-111	102	-164
Net income (loss)	6,934	2,102	201					6,816				118	134	20	1,968
Ending Balance at Dec. 31, 2013	51,058		957	25	5	0	38,890	19,235	-7,517	56		364
Ending balance at Dec. 31, 2013		29,327									-16		287	231	29,056
Stock compensation plans	299						732	-433
Repurchases and retirements of common stock	-4,251						-928	-3,323
Employee stock purchase plans	118						118
Other comprehensive income (loss)	-202	-143								-202	-143
Redemption transaction distribution		0
Dividends declared	-2,320	-1,641						-2,320							-1,641
Issuance of subsidiary shares to noncontrolling interests	11		85									11		85
Contributions from and (distributions to) noncontrolling interests, net	-132	-152	-19									-132	-152	-24
Other	-29	-13	-33				-7					-22	-12		-1
Net income (loss)	8,516	3,259	76					8,380				136	144	38	3,115
Ending Balance at Dec. 31, 2014	53,068		1,066	25	5	0	38,805	21,539	-7,517	-146		357
Ending balance at Dec. 31, 2014		$30,637									($159)		$267	$330	$30,529

Business_and_Basis_of_Presenta

Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2014
Business and Basis of Presentation	Note 1: Business and Basis of Presentation
	We are a global media and technology company with two primary businesses, Comcast Cable and NBCUniversal. We were incorporated under the laws of Pennsylvania in December 2001. Through our predecessors, we have developed, managed and operated cable systems since 1963. In 2013, we acquired General Electric Company’s (“GE”) 49% common equity interest in NBCUniversal, LLC (“NBCUniversal Holdings”) that we did not already own.
	On February 12, 2014, we entered into an agreement and plan of merger (the “merger agreement”) with Time Warner Cable Inc. (“Time Warner Cable”) whereby Time Warner Cable will become our wholly owned subsidiary (the “Time Warner Cable merger”). On April 25, 2014, in connection with the merger agreement, we entered into an agreement with Charter Communications, Inc. (“Charter”) that, among other things, would result in a net disposition of certain cable systems. See Note 5 for additional information on the Time Warner Cable merger and the agreement with Charter.
	We present our operations for Comcast Cable in one reportable business segment, referred to as Cable Communications, and our operations for NBCUniversal in four reportable business segments. The Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks segments comprise the NBCUniversal businesses (collectively, the “NBCUniversal segments”). See Note 18 for additional information on our reportable business segments.
	Our Cable Communications segment primarily manages and operates cable systems that serve residential and business customers in the United States. As of December 31, 2014, our cable systems served 22.4 million video customers, 22.0 million high-speed Internet customers and 11.2 million voice customers, with 27.0 million total customer relationships.
	Our Cable Networks segment consists primarily of a diversified portfolio of cable television networks. Our cable networks are comprised of our national cable networks, which provide a variety of entertainment, news and information, and sports content, our regional sports and news networks, our international cable networks, and our cable television production operations.
	Our Broadcast Television segment consists primarily of the NBC and Telemundo broadcast networks, our NBC and Telemundo owned local broadcast television stations, the NBC Universo (formerly mun2) national cable network, and our broadcast television production operations.
	Our Filmed Entertainment segment primarily produces, acquires, markets and distributes filmed entertainment worldwide. Our films are produced primarily under the Universal Pictures, Focus Features and Illumination names.
	Our Theme Parks segment consists primarily of our Universal theme parks in Orlando, Florida and Hollywood, California. Our Theme Parks segment also receives fees from third parties that own and operate Universal Studios Japan and Universal Studios Singapore for intellectual property licenses and other services.
	Our other business interests consist primarily of Comcast-Spectacor, which owns the Philadelphia Flyers and the Wells Fargo Center arena in Philadelphia, Pennsylvania and operates arena management-related businesses.
	Basis of Presentation
	The accompanying consolidated financial statements include all entities in which we have a controlling voting interest (“subsidiaries”) and variable interest entities (“VIEs”) required to be consolidated in accordance with generally accepted accounting principles in the United States (“GAAP”).
	We translate assets and liabilities of our foreign subsidiaries where the functional currency is the local currency, primarily the euro and the British pound, into U.S. dollars at the exchange rate as of the balance sheet date and translate revenue and expenses using average monthly exchange rates. The related translation adjustments are recorded as a component of accumulated other comprehensive income (loss). Any foreign currency transaction gains and losses are included in our consolidated statement of income.
NBCUniversal Media, LLC [Member]
Business and Basis of Presentation	Note 1: Business and Basis of Presentation
	Unless indicated otherwise, throughout these notes to the consolidated financial statements, we refer to NBCUniversal and its consolidated subsidiaries as “we,” “us” and “our.” We are one of the world’s leading media and entertainment companies that develops, produces and distributes entertainment, news and information, sports, and other content for global audiences. In 2013, Comcast acquired General Electric Company’s (“GE”) 49% common equity interest in our parent, NBCUniversal, LLC (“NBCUniversal Holdings”), that it did not already own. See Note 4 for additional information on the redemption transaction.
	We present our operations as the following four reportable business segments: Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks. See Note 17 for additional information on our reportable business segments.
	Our Cable Networks segment consists primarily of a diversified portfolio of cable television networks. Our cable networks are comprised of our national cable networks, which provide a variety of entertainment, news and information, and sports content, our regional sports and news networks, our international cable networks, and our cable television production operations.
	Our Broadcast Television segment consists primarily of the NBC and Telemundo broadcast networks, our NBC and Telemundo owned local broadcast television stations, the NBC Universo (formerly mun2) national cable network, and our broadcast television production operations.
	Our Filmed Entertainment segment primarily produces, acquires, markets and distributes filmed entertainment worldwide. Our films are produced primarily under the Universal Pictures, Focus Features and Illumination names.
	Our Theme Parks segment consists primarily of our Universal theme parks in Orlando, Florida and Hollywood, California. Our Theme Parks segment also receives fees from third parties that own and operate Universal Studios Japan and Universal Studios Singapore for intellectual property licenses and other services.
	Basis of Presentation
	The accompanying consolidated financial statements include all entities in which we have a controlling voting interest (“subsidiaries”) and variable interest entities (“VIEs”) required to be consolidated in accordance with generally accepted accounting principles in the United States (“GAAP”). Transactions between NBCUniversal and both Comcast and Comcast’s consolidated subsidiaries are reflected in these consolidated financial statements and disclosed as related party transactions when material.
	We translate assets and liabilities of our foreign subsidiaries where the functional currency is the local currency, primarily the euro and the British pound, into U.S. dollars at the exchange rate as of the balance sheet date and translate revenue and expenses using average monthly exchange rates. The related translation adjustments are recorded as a component of accumulated other comprehensive income (loss). Any foreign currency transaction gains and losses are included in our consolidated statement of income.

Accounting_Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies	Note 2: Accounting Policies
	Our consolidated financial statements are prepared in accordance with GAAP, which requires us to select accounting policies, including in certain cases industry-specific policies, and make estimates that affect the reported amount of assets, liabilities, revenue and expenses, and the related disclosure of contingent assets and contingent liabilities. Actual results could differ from these estimates. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements:
	valuation and impairment testing of cable franchise rights (see Note 9)
	film and television costs (see Note 6)
	income taxes (see Note 15)
	In addition, the following accounting policies are specific to the industries in which we operate:
	capitalization and amortization of film and television costs (see Note 6)
	installation costs for connecting customers to our cable systems (see Note 8)
	Information on our other accounting policies or methods related to our consolidated financial statements are included, where applicable, in their respective footnotes that follow. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes.
	Revenue Recognition
	Cable Communications Segment
	Our Cable Communications segment generates revenue primarily from subscriptions to our video, high-speed Internet and voice services (“cable services”) and from the sale of advertising. We recognize revenue from cable services as each service is provided. Customers are typically billed in advance on a monthly basis based on the services and features they receive and the type of equipment they use. We manage credit risk by screening applicants through the use of internal customer information, identification verification tools and credit bureau data. If a customer’s account is delinquent, various measures are used to collect outstanding amounts, including termination of the customer’s cable services. Since installation revenue obtained from the connection of customers to our cable systems is less than the related direct selling costs, we recognize revenue as connections are completed.
	As part of our distribution agreements with cable networks, we generally receive an allocation of scheduled advertising time on cable networks that our Spotlight business sells to local, regional and national advertisers. We recognize advertising revenue when the advertising is aired. In most cases, the available advertising units are sold by our sales force. In some cases, we work with representation firms as an extension of our sales force to sell a portion of the advertising units allocated to us. We also represent the advertising sales efforts of other multichannel video providers in some markets. Since we are acting as the principal in these arrangements, we report the advertising that is sold as revenue and the fees paid to representation firms and multichannel video providers as other operating and administrative expenses.
	Revenue earned from other sources, such as our home security and automation services, is recognized when services are provided or events occur. Under the terms of our cable franchise agreements, we are generally required to pay to the cable franchising authority an amount based on our gross video revenue. We normally pass these fees through to our cable services customers and classify the fees as a component of revenue with the corresponding costs included in other operating and administrative expenses.
	Cable Networks and Broadcast Television Segments
	Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to multichannel video providers, from the sale of advertising on our cable networks and related digital media properties, from the licensing of our owned programming through distribution to subscription video on demand services and various other distribution platforms, and from the sale of our owned programming electronically through digital distributors such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and related digital media properties, from the licensing of our owned programming through various distribution platforms, including to cable and broadcast networks and to subscription video on demand services, and from fees received under retransmission consent agreements. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution.
	Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which commercials are aired or viewed. In some instances, we guarantee viewer ratings for the commercials. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We record revenue from the licensing of our owned programming when the content is available for use by the licensee, and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed.
	Filmed Entertainment Segment
	Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of our owned and acquired films through various distribution platforms, and from the sale of our owned and acquired films on standard-definition video discs and Blu-ray discs (together, “DVDs”) and electronically through digital distributors. Our Filmed Entertainment segment also generates revenue from producing and licensing live stage plays, from the distribution of filmed entertainment produced by third parties, and from a movie ticketing and entertainment business. We recognize <>revenue from the distribution of films to movie theaters when the films are exhibited. We record revenue from the licensing of a film when the film is available for use by the licensee, and when certain other conditions are met. We recognize revenue from DVD sales, net of estimated returns and customer incentives, on the date that DVDs are delivered to and made available for sale by retailers.
	Theme Parks Segment
	Our Theme Parks segment generates revenue primarily from theme park attendance and per capita spending at our Universal theme parks in Orlando, Florida and Hollywood, California, as well as from licensing and other fees. We recognize <>revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the annual period following the initial activation date.
	Cable Communications Programming Expenses
	Cable Communications programming expenses are the fees we pay to license the programming we distribute to our video customers. Programming is acquired for distribution to our video customers, generally under multiyear distribution agreements, with rates typically based on the number of customers that receive the programming, channel positioning and the extent of distribution. From time to time, these contracts expire and programming continues to be provided under interim arrangements while the parties negotiate new contractual terms, sometimes with effective dates that affect prior periods. While payments are typically made under the prior contract’s terms, the amount of programming expenses recorded during these interim arrangements is based on our estimates of the ultimate contractual terms expected to be negotiated. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution.
	When our Cable Communications segment receives incentives from cable networks for the licensing of their programming, we defer a portion of these incentives, which are included in other current and noncurrent liabilities, and recognize them over the term of the contract as a reduction to programming expenses.
	Advertising Expenses
	Advertising costs are expensed as incurred.
	Cash Equivalents
	The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased.
	Derivative Financial Instruments
	We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in interest rates, foreign exchange rates and equity prices. Our objective is to manage the financial and operational exposure arising from these risks by offsetting gains and losses on the underlying exposures with gains and losses on the derivatives used to economically hedge them.
	Our derivative financial instruments are recorded in our consolidated balance sheet at fair value. See Note 7 for additional information on the derivative component of our prepaid forward sale agreements. The impact of other derivative financial instruments on our consolidated financial statements was not material for all periods presented.
	Asset Retirement Obligations
	Certain of our cable franchise agreements and lease agreements contain provisions requiring us to restore facilities or remove property in the event that the franchise or lease agreement is not renewed. We expect to continually renew our cable franchise agreements and therefore cannot reasonably estimate any liabilities associated with such agreements. A remote possibility exists that franchise agreements could be terminated unexpectedly, which could result in us incurring significant expense in complying with restoration or removal provisions. The disposal obligations related to our properties are not material to our consolidated financial statements. We do not have any significant liabilities related to asset retirements recorded in our consolidated financial statements.
NBCUniversal Media, LLC [Member]
Accounting Policies	Note 2: Accounting Policies
	Our consolidated financial statements are prepared in accordance with GAAP, which requires us to select accounting policies, including in certain cases industry-specific policies, and make estimates that affect the reported amount of assets, liabilities, revenue and expenses, and the related disclosure of contingent assets and contingent liabilities. Actual results could differ from these estimates. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements:
	revenue recognition (see below)
	film and television costs (see Note 6)
	goodwill and intangible assets (see Note 9)
	fair value of contractual obligations (see Note 11)
	In addition, the following accounting policies are specific to the industries in which we operate:
	capitalization and amortization of film and television costs (see Note 6)
	Information on our other accounting policies or methods related to our consolidated financial statements are included, where applicable, in their respective footnotes that follow. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes.
	Revenue Recognition
	Cable Networks and Broadcast Television Segments
	Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to multichannel video providers, from the sale of advertising on our cable networks and related digital media properties, from the licensing of our owned programming through distribution to subscription video on demand services and various other distribution platforms, and from the sale of our owned programming electronically through digital distributors such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and related digital media properties, from the licensing of our owned programming through various distribution platforms, including to cable and broadcast networks and to subscription video on demand services, and from fees received under retransmission consent agreements. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution.
	Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which commercials are aired or viewed. In some instances, we guarantee viewer ratings for the commercials. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We record revenue from the licensing of our owned programming when the content is available for use by the licensee, and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed.
	Filmed Entertainment Segment
	Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of our owned and acquired films through various distribution platforms, and from the sale of our owned and acquired films on standard-definition video discs and Blu-ray discs (together, “DVDs”) and electronically through digital distributors. Our Filmed Entertainment segment also generates revenue from producing and licensing live stage plays, from the distribution of filmed entertainment produced by third parties, and from a movie ticketing and entertainment business. We recognize <>revenue from the distribution of films to movie theaters when the films are exhibited. We record revenue from the licensing of a film when the film is available for use by the licensee, and when certain other conditions are met. We recognize revenue from DVD sales, net of estimated returns and customer incentives, on the date that DVDs are delivered to and made available for sale by retailers.
	Theme Parks Segment
	Our Theme Parks segment generates revenue primarily from theme park attendance and per capita spending at our Universal theme parks in Orlando, Florida and Hollywood, California, as well as from licensing and other fees. We recognize <>revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the annual period following the initial activation date.
	Advertising Expenses
	Advertising costs are expensed as incurred.
	Cash Equivalents
	The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased.
	Derivative Financial Instruments
	We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in foreign exchange rates and interest rates. Our objective is to manage the financial and operational exposure arising from these risks by offsetting gains and losses on the underlying exposures with gains and losses on the derivatives used to economically hedge them.
	Our derivative financial instruments are recorded in our consolidated balance sheet at fair value. The impact of our derivative financial instruments on our consolidated financial statements was not material for all periods presented.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2014
Recent Accounting Pronouncements	Note 3: Recent Accounting Pronouncements
	Discontinued Operations
	In April 2014, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to discontinued operations. The updated accounting guidance provides a narrower definition of discontinued operations than existing GAAP. The updated accounting guidance requires that only disposals of components of an entity, or groups of components, that represent a strategic shift that has or will have a material effect on the reporting entity’s operations be reported in the financial statements as discontinued operations. The updated accounting guidance also provides guidance on the financial statement presentations and disclosures of discontinued operations. The updated accounting guidance will be effective prospectively for us on January 1, 2015.
	Revenue Recognition
	In May 2014, the FASB and the International Accounting Standards Board updated the accounting guidance related to revenue recognition. The updated accounting guidance provides a single, contract-based revenue recognition model to help improve financial reporting by providing clearer guidance on when an entity should recognize revenue, and by reducing the number of standards to which entities have to refer. The updated accounting guidance will be effective for us on January 1, 2017, and early adoption is not permitted. The updated accounting guidance provides companies with alternative methods of adoption. We are currently in the process of determining the impact that the updated accounting guidance will have on our consolidated financial statements and our method of adoption.
NBCUniversal Media, LLC [Member]
Recent Accounting Pronouncements	Note 3: Recent Accounting Pronouncements
	Discontinued Operations
	In April 2014, the Financial Accounting Standards Board (“FASB”) updated the accounting guidance related to discontinued operations. The updated accounting guidance provides a narrower definition of discontinued operations than existing GAAP. The updated accounting guidance requires that only disposals of components of an entity, or groups of components, that represent a strategic shift that has or will have a material effect on the reporting entity’s operations be reported in the financial statements as discontinued operations. The updated accounting guidance also provides guidance on the financial statement presentations and disclosures of discontinued operations. The updated accounting guidance will be effective prospectively for us on January 1, 2015.
	Revenue Recognition
	In May 2014, the FASB and the International Accounting Standards Board updated the accounting guidance related to revenue recognition. The updated accounting guidance provides a single, contract-based revenue recognition model to help improve financial reporting by providing clearer guidance on when an entity should recognize revenue, and by reducing the number of standards to which entities have to refer. The updated accounting guidance will be effective for us on January 1, 2017, and early adoption is not permitted. The updated accounting guidance provides companies with alternative methods of adoption. We are currently in the process of determining the impact that the updated accounting guidance will have on our consolidated financial statements and our method of adoption.

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share
Earnings Per Share	Note 4: Earnings Per Share
	Computation of Diluted EPS
				2014					2013					2012
	Year ended December 31 (in millions, except per share data)			Net Income Attributable to Comcast Corporation	Shares		Per Share Amount		Net Income Attributable to Comcast Corporation	Shares		Per Share Amount		Net Income Attributable to Comcast Corporation	Shares		Per Share Amount
	Basic EPS attributable to Comcast Corporation shareholders		$	8,380	2,583	$	3.24	$	6,816	2,625	$	2.6	$	6,203	2,678	$	2.32
	Effect of dilutive securities:
		Assumed exercise or issuance of shares relating to stock plans			37					40					39
	Diluted EPS attributable to Comcast
		Corporation shareholders	$	8,380	2,620	$	3.2	$	6,816	2,665	$	2.56	$	6,203	2,717	$	2.28
	Diluted earnings per common share attributable to Comcast Corporation shareholders (“diluted EPS”) considers the impact of potentially dilutive securities using the treasury stock method. Our potentially dilutive securities include potential common shares related to our stock options and our restricted share units (“RSUs”). Diluted EPS excludes the impact of potential common shares related to our stock options in periods in which the combination of the option exercise price and the associated unrecognized compensation expense is greater than the average market price of our Class A common stock or our Class A Special common stock, as applicable.
	The amount of potential common shares related to our share-based compensation plans that were excluded from diluted EPS because their effect would have been antidilutive was not material for 2014, 2013 and 2012.

Significant_Transactions

Significant Transactions	12 Months Ended
	Dec. 31, 2014
Significant Transactions	Note 5: Significant Transactions
	2014
	Time Warner Cable Merger
	On February 12, 2014, we entered into the merger agreement with Time Warner Cable. Time Warner Cable is among the largest providers of video, high-speed Internet and voice services in the United States, located mainly in five geographic areas: New York State (including New York City), the Carolinas, the Midwest (including Ohio, Kentucky and Wisconsin), Southern California (including Los Angeles) and Texas. Time Warner Cable stockholders will receive, in exchange for each share of Time Warner Cable common stock owned immediately prior to the Time Warner Cable merger, 2.875 shares of our Class A common stock. Because the exchange ratio was fixed at the time of the merger agreement and the market value of our Class A common stock will continue to fluctuate, the number of shares of Class A common stock to be issued and the total value of the consideration exchanged will not be determinable until the closing date. The Time Warner Cable merger was approved by both Comcast shareholders and Time Warner Cable stockholders in October 2014. The Time Warner Cable merger remains subject to regulatory approval and other customary conditions and is expected to close in early 2015.
	Divestiture Transactions
	The terms of the merger agreement contemplated that we would divest systems serving up to approximately 3 million of our video customers following the Time Warner Cable merger in order to obtain applicable regulatory approvals. As a result of this commitment, on April 25, 2014, we entered into an agreement with Charter that, if consummated, would satisfy the divestiture undertaking. Under this agreement, following the close of the Time Warner Cable merger and subject to various conditions, we agreed to divest certain cable systems through three transactions: (1) a spin-off of certain of our existing cable systems (the “spin-off transaction”) into a newly formed public entity (“SpinCo”), (2) an exchange of certain former Time Warner Cable cable systems for Charter cable systems, and (3) a sale to Charter of certain former Time Warner Cable cable systems for cash (collectively, the “divestiture transactions”).
	In connection with and prior to the spin-off transaction, it is expected that SpinCo would incur new debt. The debt would consist of credit facilities to fund cash distributions to us and notes which SpinCo would issue to us. These notes would enable us to complete a debt-for-debt exchange where financial institutions would exchange a portion of our debt securities for the new SpinCo notes, which would effectively retire a portion of our debt. In the spin-off transaction, we would distribute the common stock of SpinCo pro rata to the holders of all of our outstanding common stock as of the record date, which would occur following the close of the Time Warner Cable merger. After the spin-off transaction, a newly formed, wholly owned indirect subsidiary of Charter would merge with and into Charter with the effect that all shares of Charter would be converted into shares of a new holding company, which would survive as the publicly traded parent company of Charter (“New Charter”). New Charter would then acquire an interest in SpinCo by issuing New Charter stock in exchange for a portion of the outstanding SpinCo stock, following which it is expected that Comcast shareholders would own approximately 67% of SpinCo and New Charter would own approximately 33% of SpinCo. In addition, Comcast shareholders would own New Charter stock as a result of the exchange of outstanding SpinCo stock with New Charter, although the actual number of shares would depend on a number of factors, some of which would not be determinable until the completion of the divestiture transactions. Following the close of the divestiture transactions, we would no longer have any ownership interest in SpinCo.
	The close of the divestiture transactions is subject to the completion of the Time Warner Cable merger, the SpinCo financing transactions, approval by Charter’s stockholders, regulatory approvals and other customary conditions. The Time Warner Cable merger and the divestiture transactions are subject to separate conditions, and the Time Warner Cable merger can be completed regardless of whether the divestiture transactions are ultimately completed. The closing of the divestiture transactions is expected to occur 30 to 60 days following the close of the Time Warner Cable merger.
	Transactions-Related Expenses
	In connection with the Time Warner Cable merger and the divestiture transactions, we have incurred incremental expenses of $237 million in 2014 which included legal, accounting and valuation services and advisory fees, all of which are reflected in other operating and administrative expenses.
	2013
	NBCUniversal Redemption Transaction
	On March 19, 2013, we acquired GE’s 49% common equity interest in NBCUniversal Holdings that we did not already own for approximately $16.7 billion (the “NBCUniversal redemption transaction”). In addition to the NBCUniversal redemption transaction, NBCUniversal purchased from GE certain properties NBCUniversal occupies at 30 Rockefeller Plaza in New York City and CNBC’s headquarters in Englewood Cliffs, New Jersey for $1.4 billion.
	The total consideration for these transactions consisted of $11.4 billion of cash on hand; $4 billion of senior debt securities issued by NBCUniversal Enterprise, Inc. (“NBCUniversal Enterprise”), a holding company that we control and consolidate following the close of the NBCUniversal redemption transaction whose principal assets are its interests in NBCUniversal Holdings; $750 million of cash funded through our commercial paper program; $1.25 billion of borrowings under NBCUniversal Enterprise’s credit facility, which replaced NBCUniversal’s credit facility; and $725 million aggregate liquidation preference of Series A cumulative preferred stock of NBCUniversal Enterprise. See Note 20 for additional information on our cross-guarantee structure.
	Because we maintained control of NBCUniversal Holdings, the difference between the consideration transferred and the recorded value of GE’s 49% redeemable noncontrolling common equity interest, and the related tax impacts, were recorded to additional paid-in capital.
	The NBCUniversal Enterprise preferred stock pays dividends at a fixed rate of 5.25% per annum. The holders have the right to cause NBCUniversal Enterprise to redeem their shares at a price equal to the liquidation preference plus accrued but unpaid dividends for a 30 day period beginning on March 19, 2020 and thereafter on every third anniversary of such date (each such date, a “put date”). Shares of preferred stock can be called for redemption by NBCUniversal Enterprise at a price equal to the liquidation preference plus accrued but unpaid dividends one year following each put date applicable to such shares. Because certain of these redemption provisions are outside of our control, the NBCUniversal Enterprise preferred stock is presented outside of equity under the caption “redeemable noncontrolling interests and redeemable subsidiary preferred stock” in our consolidated balance sheet. Its initial value was based on the liquidation preference of the preferred stock and is adjusted for accrued but unpaid dividends. As of December 31, 2014 and 2013, the fair value of the NBCUniversal Enterprise redeemable subsidiary preferred stock was $751 million and $741 million, respectively. The estimated fair values are based on Level 2 inputs that use pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument.
NBCUniversal Media, LLC [Member]
Significant Transactions	Note 4: Significant Transactions
	2013
	Redemption Transaction
	On March 19, 2013, Comcast acquired GE’s 49% common equity interest in NBCUniversal Holdings that it did not already own for approximately $16.7 billion (the “redemption transaction”). In addition to the redemption transaction, we purchased from GE certain properties we occupy at 30 Rockefeller Plaza in New York City and CNBC’s headquarters in Englewood Cliffs, New Jersey for $1.4 billion.
	The total consideration for these transactions consisted of $11.4 billion of cash on hand (of which we funded $4.6 billion); $4 billion of senior debt securities issued by NBCUniversal Enterprise, Inc. (“NBCUniversal Enterprise”), a holding company whose principal assets are its interests in NBCUniversal Holdings; $750 million of cash funded through Comcast’s commercial paper program; $1.25 billion of borrowings under NBCUniversal Enterprise’s credit facility, which replaced our credit facility; and $725 million aggregate liquidation preference of Series A cumulative preferred stock of NBCUniversal Enterprise. After the close of the transaction, GE sold the interests in NBCUniversal Enterprise’s senior debt securities and preferred stock it acquired in the redemption transaction to unaffiliated third parties.
	Following the close of the redemption transaction, Comcast owns 96% of NBCUniversal Holdings’ common units and NBCUniversal Enterprise owns the remaining 4%. NBCUniversal Enterprise is now a consolidated subsidiary of Comcast, but we do not have any ownership interests in NBCUniversal Enterprise. NBCUniversal Enterprise also owns all of NBCUniversal Holdings’ preferred units with a $9.4 billion aggregate liquidation preference. NBCUniversal Holdings is required to make quarterly payments to NBCUniversal Enterprise at an initial rate of 8.25% per annum on the $9.4 billion aggregate liquidation preference of the preferred units. On March 1, 2018, and thereafter on every fifth anniversary of such date, this rate will reset to 7.44% plus the yield on actively traded United States Treasury securities having a 5 year maturity. NBCUniversal Holdings has the right to redeem all of the preferred units during the 30 day period beginning on March 1, 2018, and NBCUniversal Enterprise has the right to cause NBCUniversal Holdings to redeem 15% of its preferred units during the 30 day period beginning on March 19, 2020. The price and units in a redemption initiated by either party will be based on the liquidation preference plus accrued but unpaid dividends and adjusted, in the case of an exercise of NBCUniversal Enterprise’s right, to the extent the equity value of NBCUniversal Holdings is less than the liquidation preference. Our cash flows are, and will continue to be, the primary source of funding for the required payments and for any future redemption of the NBCUniversal Holdings preferred units.

Related_Party_Transactions

Related Party Transactions (NBCUniversal Media, LLC [Member])	12 Months Ended
	Dec. 31, 2014
NBCUniversal Media, LLC [Member]
Related Party Transactions	Note 5: Related Party Transactions
	In the ordinary course of our business, we enter into transactions with Comcast.
	We generate revenue from Comcast primarily from the distribution of our cable network programming and, to a lesser extent, the sale of advertising and the licensing of our owned programming, and we incur expenses primarily related to various support services provided by Comcast to us.
	In 2013, as part of the Comcast cash management process, we and Comcast entered into a revolving credit agreement under which we can borrow up to $3 billion from Comcast and Comcast can borrow up to $3 billion from us. Amounts owed by us to Comcast under the revolving credit agreement, including accrued interest, are presented under the caption “note payable to Comcast” in our consolidated balance sheet. The revolving credit agreements bear interest at floating rates equal to the interest rate under the Comcast and Comcast Cable Communications, LLC revolving credit facility (the “Comcast revolving credit facility”). The interest rate on the Comcast revolving credit facility consists of a base rate plus a borrowing margin that is determined based on Comcast’s credit rating. As of December 31, 2014, the borrowing margin for London Interbank Offered Rate-based borrowings was 1.00%.
	In addition, Comcast is the counterparty to one of our contractual obligations. As of both December 31, 2014 and 2013, the carrying value of the liability associated with this contractual obligation was $383 million.
	The following tables present transactions with Comcast and its consolidated subsidiaries that are included in our consolidated financial statements.
	Consolidated Balance Sheet
	December 31 (in millions)			2014			2013
	Transactions with Comcast and Consolidated Subsidiaries
		Receivables, net		$	229		$	228
		Accounts payable and accrued expenses related to trade creditors		$	47		$	56
		Accrued expenses and other current liabilities		$	8		$	37
		Note payable to Comcast		$	865		$	799
		Other noncurrent liabilities		$	383		$	383
	Consolidated Statement of Income
	Year ended December 31 (in millions)			2014		2013		2012
	Transactions with Comcast and Consolidated Subsidiaries
		Revenue	$	1,315	$	1,262	$	1,228
		Operating costs and expenses	$	-162	$	-190	$	-175
		Other income (expense)	$	-43	$	-	$	-
	Distributions to NBCUniversal Holdings
	In addition to the transactions presented in the table above, we make distributions to NBCUniversal Holdings on a periodic basis to enable its owners to meet their obligations to pay taxes on taxable income generated by our businesses. We also make quarterly distributions to NBCUniversal Holdings to enable it to make its required quarterly payments to NBCUniversal Enterprise at an initial annual rate of 8.25% on the $9.4 billion aggregate liquidation preference of its preferred units. These distributions are presented under the caption “distributions to member” in our consolidated statement of cash flows. Following the close of the redemption transaction, none of these distributions to NBCUniversal Holdings are attributable to GE.
	In connection with the redemption transaction, we also made a distribution of $3.2 billion to NBCUniversal Holdings to fund a portion of the redemption transaction. This distribution is presented separately in our consolidated statement of cash flows.
	Transactions with GE
	Following the close of the redemption transaction and the subsequent sale of NBCUniversal Enterprise’s preferred stock and senior notes by GE to unaffiliated third parties in March 2013, we no longer consider GE to be a related party.
	In February 2013, Comcast closed an agreement with GE, General Electric Capital Corporation (“GECC”) and LIN TV under which, among other things, we purchased a note held by Station Venture Holdings, LLC (“Station Venture”) from GECC for $602 million, which effectively settled a liability of $482 million that had been recorded in the allocation of purchase price associated with Comcast’s acquisition of a controlling interest in NBCUniversal Holdings in 2011 (the “joint venture transaction”). Due to the related party nature of this transaction, the excess of the purchase price of the Station Venture note over the recorded amount of the liability was recorded to member’s capital. Other than the Station Venture transaction and dividend payments to GE that are included in our consolidated statement of changes in equity and our consolidated statement of cash flows, the amounts related to our transactions with GE and its consolidated subsidiaries that occurred prior to the close of the redemption transaction were not material.

Film_and_Television_Costs

Film and Television Costs	12 Months Ended
	Dec. 31, 2014
Film And Television Costs Disclosure [Text Block]	Note 6: Film and Television Costs
	December 31 (in millions)			2014		2013
	Film Costs:
		Released, less amortization	$	1,371	$	1,630
		Completed, not released		71		70
		In production and in development		1,189		658
				2,631		2,358
	Television Costs:
		Released, less amortization		1,273		1,155
		In production and in development		505		370
				1,778		1,525
	Programming rights, less amortization			2,157		2,039
				6,566		5,922
	Less: Current portion of programming rights			839		928
	Film and television costs		$	5,727	$	4,994
	Based on our estimates of the ratio of the current period’s actual revenue to the estimated total remaining gross revenue from all sources (“ultimate revenue”), as of December 31, 2014, approximately $1.3 billion of film and television costs associated with our original film and television productions that have been released, or completed and not yet released, are expected to be amortized during 2015. Approximately 86% of unamortized film and television costs for our released productions, excluding amounts allocated to acquired libraries, are expected to be amortized through 2017.
	As of December 31, 2014, acquired film and television libraries, which are included within the “released, less amortization” captions in the table above, had remaining unamortized costs of $570 million. These costs are generally amortized over a period not to exceed 20 years, and approximately 51% of these costs are expected to be amortized through 2017.
	Capitalization of Film and Television Costs
	We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expense. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes such costs in the same ratio as the associated ultimate revenue. Estimates of total revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television costs, including acquired film and television libraries, are stated at the lower of unamortized cost or fair value. We do not capitalize costs related to the distribution of a film to movie theaters or the licensing or sale of a film or television production, which are primarily costs associated with the marketing and distribution of film and television programming.
	In determining the estimated lives and method of amortization of acquired film and television libraries, we generally use the method and the life that most closely follow the undiscounted cash flows over the estimated life of the asset.
	Upon the occurrence of an event or a change in circumstance that was known or knowable as of the balance sheet date and that indicates the fair value of a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value.
	We enter into cofinancing arrangements with third parties to jointly finance or distribute certain of our film productions. Cofinancing arrangements can take various forms, but in most cases involve the grant of an economic interest in a film to an investor. The number of investors and the terms of these arrangements can vary, although investors generally assume full risk for the portion of the film acquired in these arrangements. We account for the proceeds received from a third-party investor under these arrangements as a reduction to our capitalized film costs. In these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expense to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life.
	We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is available for use. We amortize capitalized programming costs as the associated programs are broadcast. We amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated total remaining revenue or under the terms of the contract.
	Acquired programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Acquired programming used in our Cable Networks segment is primarily tested on a channel basis for impairment, whereas acquired programming used in our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expense.
NBCUniversal Media, LLC [Member]
Film And Television Costs Disclosure [Text Block]	Note 6: Film and Television Costs
	December 31 (in millions)			2014		2013
	Film Costs:
		Released, less amortization	$	1,371	$	1,630
		Completed, not released		71		70
		In production and in development		1,189		658
				2,631		2,358
	Television Costs:
		Released, less amortization		1,273		1,155
		In production and in development		505		370
				1,778		1,525
	Programming rights, less amortization			2,130		2,003
				6,539		5,886
	Less: Current portion of programming rights			825		903
	Film and television costs		$	5,714	$	4,983
	Based on our estimates of the ratio of the current period’s actual revenue to the estimated total remaining gross revenue from all sources (“ultimate revenue”), as of December 31, 2014, approximately $1.3 billion of film and television costs associated with our original film and television productions that have been released, or completed and not yet released, are expected to be amortized during 2015. Approximately 86% of unamortized film and television costs for our released productions, excluding amounts allocated to acquired libraries, are expected to be amortized through 2017.
	As of December 31, 2014, acquired film and television libraries, which are included within the “released, less amortization” captions in the table above, had remaining unamortized costs of $570 million. These costs are generally amortized over a period not to exceed 20 years, and approximately 51% of these costs are expected to be amortized through 2017.
	Capitalization of Film and Television Costs
	We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expense. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes such costs in the same ratio as the associated ultimate revenue. Estimates of total revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television costs, including acquired film and television libraries, are stated at the lower of unamortized cost or fair value. We do not capitalize costs related to the distribution of a film to movie theaters or the licensing or sale of a film or television production, which are primarily costs associated with the marketing and distribution of film and television programming.
	In determining the estimated lives and method of amortization of acquired film and television libraries, we generally use the method and the life that most closely follow the undiscounted cash flows over the estimated life of the asset.
	Upon the occurrence of an event or a change in circumstance that was known or knowable as of the balance sheet date and that indicates the fair value of a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value.
	We enter into cofinancing arrangements with third parties to jointly finance or distribute certain of our film productions. Cofinancing arrangements can take various forms, but in most cases involve the grant of an economic interest in a film to an investor. The number of investors and the terms of these arrangements can vary, although investors generally assume full risk for the portion of the film acquired in these arrangements. We account for the proceeds received from a third-party investor under these arrangements as a reduction to our capitalized film costs. In these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expense to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life.
	We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is available for use. We amortize capitalized programming costs as the associated programs are broadcast. We amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated total remaining revenue or under the terms of the contract.
	Acquired programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Acquired programming used in our Cable Networks segment is primarily tested on a channel basis for impairment, whereas acquired programming used in our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expense.

Investments

Investments	12 Months Ended
	Dec. 31, 2014
Investments	Note 7: Investments
	December 31 (in millions)			2014		2013
	Fair Value Method		$	662	$	4,345
	Equity Method:
		The Weather Channel		335		333
		Hulu		167		187
		Other		517		469
				1,019		989
	Cost Method:
		AirTouch		1,568		1,553
		Other		488		456
				2,056		2,009
	Total investments			3,737		7,343
	Less: Current investments			602		3,573
	Noncurrent investments		$	3,135	$	3,770
	Investment Income (Loss), Net
	Year ended December 31 (in millions)			2014		2013		2012
	Gains on sales and exchanges of investments, net		$	192	$	484	$	30
	Investment impairment losses			-50		-29		-24
	Unrealized gains on securities underlying prepaid forward sale agreements			66		1,601		1,159
	Mark to market adjustments on derivative component of prepaid forward sale
		agreements and indexed debt instruments		-56		-1,604		-1,071
	Interest and dividend income			116		111		119
	Other, net			28		13		6
	Investment income (loss), net		$	296	$	576	$	219
	Fair Value Method
	We classify publicly traded investments that are not accounted for under the equity method as available-for-sale (“AFS”) or trading securities and record them at fair value. For AFS securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of other comprehensive income (loss), except when we consider declines in value to be other than temporary. For trading securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of investment income (loss), net. We recognize realized gains and losses associated with our fair value method investments using the specific identification method. We classify the cash flows related to purchases of and proceeds from the sale of trading securities based on the nature of the securities and the purpose for which they were acquired.
	As of December 31, 2014 and 2013, the majority of our fair value method investments were equity securities that we account for as trading securities and were held as collateral related to our obligations under prepaid forward sale agreements.
	Prepaid Forward Sale Agreements
	December 31 (in millions)			2014		2013
	Assets:
		Fair value equity securities held as collateral	$	523	$	3,959
	Liabilities:
		Obligations under prepaid forward sale agreements	$	119	$	811
		Derivative component of prepaid forward sale agreements		356		2,800
	Total liabilities		$	475	$	3,611
	During 2014, we settled $3.2 billion of obligations under certain of our prepaid forward sale agreements by delivering equity securities. As of December 31, 2014 and 2013, the carrying value of our remaining prepaid forward sale obligations approximated their fair value. The estimated fair values are based on Level 2 inputs that use pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument. The remaining obligations related to these investments matured in February 2015 and were settled by delivering equity securities.
	The derivative component of the prepaid forward sale agreements are equity derivative financial instruments embedded in the related contracts, which we use to manage our exposure to and benefits from price fluctuations in the common stock of the related investments. For these derivative financial instruments, we separate the derivative component from the host contract and record the change in its value each period to investment income (loss), net.
	Liberty Media
	In October 2013, Liberty Media Corporation (“Liberty Media”) redeemed 6.3 million shares of Liberty Media Series A common stock (“Liberty stock”) that had been held by us as collateral under certain of our prepaid forward sale agreements in exchange for all of the equity of a subsidiary of Liberty Media. The fair value of the Liberty stock at the date of the close of the transaction was $937 million. The assets of the subsidiary of Liberty Media included cash of $417 million, Liberty Media’s interests in one of NBCUniversal’s contractual obligations and a wholly owned operating subsidiary, Leisure Arts, Inc. Following the close of this transaction, we now consolidate the subsidiary transferred to us, and the liability associated with NBCUniversal’s contractual obligation is eliminated in consolidation.
	Clearwire LLC
	In July 2013, in connection with Sprint Communications, Inc.’s (“Sprint”) acquisition of Clearwire Corporation (“Clearwire”), Sprint acquired our investment of 89 million Class A shares of Clearwire for $443 million. As a result, we recognized a pretax gain of $443 million in our consolidated statement of income, which represented the recognition of cumulative unrealized gains previously recorded in accumulated other comprehensive income (loss).
	Equity Method
	We use the equity method to account for investments in which we have the ability to exercise significant influence over the investee’s operating and financial policies or where we hold significant partnership or LLC interests. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share of the investee’s net income or loss after the date of investment, (2) amortization of the recorded investment that exceeds our share of the book value of the investee’s net assets, (3) additional contributions made and dividends received, and (4) impairments resulting from other-than-temporary declines in fair value. For some investments, we record our share of the investee’s net income or loss one quarter in arrears due to the timing of our receipt of such information. Gains or losses on the sale of equity method investments are recorded to other income (expense), net. If an equity method investee were to issue additional securities that would change our proportionate share of the entity, we would recognize the change, if any, as a gain or loss in our consolidated statement of income.
	The Weather Channel
	In June 2013, we received a distribution from The Weather Channel Holding Corp. (“The Weather Channel”) of $152 million, of which $128 million was recorded as a return of our investment in The Weather Channel and included under the caption “return of capital from investees” in our consolidated statement of cash flows.
	Hulu
	In July 2013, we entered into an agreement to provide capital contributions totaling $247 million to Hulu, LLC (“Hulu”), which we had previously accounted for as a cost method investment. This represented an agreement to provide our first capital contribution to Hulu since we acquired our interest in it as part of our acquisition of a controlling interest in NBCUniversal Holdings in 2011 (the “NBCUniversal transaction”); therefore, we began to apply the equity method of accounting for this investment. The change in the method of accounting for this investment required us to recognize our proportionate share of Hulu’s accumulated losses from the date of the NBCUniversal transaction through July 2013.
	Cost Method
	We use the cost method to account for investments not accounted for under the fair value method or the equity method.
	AirTouch Communications, Inc.
	We hold two series of preferred stock of AirTouch Communications, Inc. (“AirTouch”), a subsidiary of Verizon Communications Inc., which are redeemable in April 2020. As of both December 31, 2014 and 2013, the estimated fair value of the AirTouch preferred stock was $1.7 billion.
	The dividend and redemption activity of the AirTouch preferred stock determines the dividend and redemption payments associated with substantially all of the preferred shares issued by one of our consolidated subsidiaries, which is a VIE. The subsidiary has three series of preferred stock outstanding with an aggregate redemption value of $1.75 billion. Substantially all of the AirTouch preferred stock is redeemable in April 2020 at a redemption value of $1.65 billion. As of December 31, 2014 and 2013, the two redeemable series of subsidiary preferred shares were recorded at $1.6 billion and $1.5 billion, respectively, and those amounts are included in other noncurrent liabilities. As of both December 31, 2014 and 2013, the redeemable subsidiary preferred shares had an estimated fair value of $1.7 billion. The estimated fair values of the AirTouch preferred stock and redeemable subsidiary preferred shares are based on Level 2 inputs that use pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument. The one nonredeemable series of subsidiary preferred shares was recorded at $100 million as of both December 31, 2014 and 2013, and those amounts are included in noncontrolling interests in our consolidated balance sheet. The carrying amount of the nonredeemable subsidiary preferred stock approximates its fair value.
	Impairment Testing of Investments
	We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. For our nonpublic investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. If an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. For our AFS and cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), net. During 2013, we recorded $249 million of impairment charges to our equity method investments, which primarily related to a regional sports cable network based in Houston, Texas.
NBCUniversal Media, LLC [Member]
Investments	Note 7: Investments
	December 31 (in millions)			2014		2013
	Fair Value Method		$	10	$	11
	Equity Method:
		The Weather Channel		335		333
		Hulu		167		187
		Other		338		332
				840		852
	Cost Method			32		21
	Total investments		$	882	$	884
	Equity Method
	We use the equity method to account for investments in which we have the ability to exercise significant influence over the investee’s operating and financial policies or where we hold significant partnership or LLC interests. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share of the investee’s net income or loss after the date of investment, (2) amortization of the recorded investment that exceeds our share of the book value of the investee’s net assets, (3) additional contributions made and dividends received, and (4) impairments resulting from other-than-temporary declines in fair value. Gains or losses on the sale of equity method investments are recorded to other income (expense), net. If an equity method investee were to issue additional securities that would change our proportionate share of the entity, we would recognize the change, if any, as a gain or loss in our consolidated statement of income.
	The Weather Channel
	In June 2013, we received a distribution from The Weather Channel Holding Corp. (“The Weather Channel”) of $152 million, of which $128 million was recorded as a return of our investment in The Weather Channel and included under the caption “return of capital from investees” in our consolidated statement of cash flows.
	Hulu
	In July 2013, we entered into an agreement to provide capital contributions totaling $247 million to Hulu, LLC (“Hulu”), which we had previously accounted for as a cost method investment. This represented an agreement to provide our first capital contribution to Hulu since Comcast acquired its interest in Hulu as part of the joint venture transaction; therefore, we began to apply the equity method of accounting for this investment. The change in the method of accounting for this investment required us to recognize our proportionate share of Hulu’s accumulated losses from the date of the joint venture transaction through July 2013.
	Cost Method
	We use the cost method to account for investments not accounted for under the fair value method or the equity method
	Impairment Testing of Investments
	We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. For our nonpublic investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. If an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. For our available-for-sale securities and cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), net. During 2013, we recorded $249 million of impairment charges to our equity method investments, which primarily related to a regional sports cable network based in Houston, Texas.

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2014
Property and Equipment	Note 8: Property and Equipment
	December 31 (in millions)	Weighted-Average Original Useful LifeAs of December 31, 2014			2014		2013
	Cable distribution system	11	years	$	31,655	$	30,498
	Customer premise equipment	6	years		27,086		25,949
	Other equipment	6	years		7,860		6,826
	Buildings and leasehold improvements	22	years		8,650		8,057
	Land		N/A		1,112		1,084
	Property and equipment, at cost				76,363		72,414
	Less: Accumulated depreciation				45,410		42,574
	Property and equipment, net			$	30,953	$	29,840
	Property and equipment are stated at cost. We capitalize improvements that extend asset lives and expense repairs and maintenance costs as incurred. We record depreciation using the straight-line method over the asset’s estimated useful life. For assets that are sold or retired, we remove the applicable cost and accumulated depreciation and, unless the gain or loss on disposition is presented separately, we recognize it as a component of depreciation expense.
	We capitalize the costs associated with the construction of and improvements to our cable transmission and distribution facilities, costs associated with acquiring and deploying new customer premise equipment, and costs associated with installation of our services in accordance with accounting guidance related to cable television companies. Costs capitalized include all direct labor and materials, as well as various indirect costs. All costs incurred in connection with subsequent disconnects and reconnects are expensed as they are incurred.
	We evaluate the recoverability of our property and equipment whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of depreciation expense.
	Acquisitions of Real Estate Properties
	Real estate acquisitions in 2013 included NBCUniversal’s purchase from GE of certain properties NBCUniversal occupies at 30 Rockefeller Plaza in New York City and CNBC’s headquarters in Englewood Cliffs, New Jersey. The CNBC property was previously recorded as a capital lease in our consolidated balance sheet. Other purchases in 2013 included NBCUniversal’s acquisition of a business whose primary asset is a property located at 10 Universal City Plaza, which is adjacent to our Universal theme park in Hollywood, California, and our acquisition of an 80% interest in a business whose primary asset is our corporate headquarters in Philadelphia, Pennsylvania. These purchases resulted in increases in 2013 of $2.2 billion in property and equipment, which are included, as applicable, within the captions “buildings and leasehold improvements” and “land” in the table above.
NBCUniversal Media, LLC [Member]
Property and Equipment	Note 8: Property and Equipment
	December 31 (in millions)	Weighted-Average Original Useful LifeAs of December 31, 2014			2014		2013
	Buildings and leasehold improvements	21	years	$	5,780	$	5,239
	Furniture, fixtures and equipment	7	years		2,930		2,383
	Construction in process		N/A		775		828
	Land		N/A		820		799
	Property and equipment, at cost				10,305		9,249
	Less: Accumulated depreciation				2,167		1,599
	Property and equipment, net			$	8,138	$	7,650
	Property and equipment are stated at cost. We capitalize improvements that extend asset lives and expense repairs and maintenance costs as incurred. We record depreciation using the straight-line method over the asset’s estimated useful life. For assets that are sold or retired, we remove the applicable cost and accumulated depreciation and, unless the gain or loss on disposition is presented separately, we recognize it as a component of depreciation expense.
	We evaluate the recoverability of our property and equipment whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of depreciation expense.
	Acquisitions of Real Estate Properties
	Real estate acquisitions in 2013 included our purchase from GE of certain properties we occupy at 30 Rockefeller Plaza in New York City and CNBC’s headquarters in Englewood Cliffs, New Jersey. The CNBC property was previously recorded as a capital lease in our consolidated balance sheet. Other purchases in 2013 included our acquisition of a business whose primary asset is a property located at 10 Universal City Plaza, which is adjacent to our Universal theme park in Hollywood, California. These purchases resulted in increases in 2013 of $1.7 billion in property and equipment, which are included, as applicable, within the captions “buildings and leasehold improvements” and “land” in the table above.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets	Note 9: Goodwill and Intangible Assets
	Goodwill
					NBCUniversal
	(in millions)			Cable Communications		Cable Networks		Broadcast Television		Filmed Entertainment		Theme Parks		Corporate and Other		Total
	Balance, December 31, 2012		$	12,206	$	13,026	$	761	$	1	$	982	$	9	$	26,985
	Acquisitions			-		39		3		-		-		-		42
	Adjustments			-		65		5		-		-		1		71
	Balance, December 31, 2013			12,206		13,130		769		1		982		10		27,098
	Acquisitions			11		20		-		15		-		181		227
	Adjustments(a)			-		-202		-2		195		-		-		-9
	Balance, December 31, 2014		$	12,217	$	12,948	$	767	$	211	$	982	$	191	$	27,316
	(a) Adjustments to goodwill in 2014 were primarily related to the reclassification of Fandango, our movie ticketing and entertainment business, from our Cable Networks segment to our Filmed Entertainment segment.
	We assess the recoverability of our goodwill annually, or more frequently whenever events or substantive changes in circumstances indicate that the carrying amount of a reporting unit may exceed its fair value. We test goodwill for impairment at the reporting unit level. To determine our reporting units, we evaluate the components one level below the segment level and we aggregate the components if they have similar economic characteristics. As a result of this assessment, our reporting units are the same as our five reportable segments. We evaluate the determination of our reporting units used to test for impairment periodically or whenever events or substantive changes in circumstances occur. The assessment of recoverability may first consider qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. The quantitative assessment considers if the carrying amount of a reporting unit exceeds its fair value, in which case an impairment charge is recorded to the extent the carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
	Intangible Assets
						2014				2013
	December 31 (in millions)		Weighted-Average Original Useful Life as of December 31, 2014			Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
	Indefinite-Lived Intangible Assets:
		Franchise rights		N/A	$	59,364			$	59,364
		Trade names		N/A		3,083				3,089
		FCC licenses		N/A		651				652
	Finite-Lived Intangible Assets:
		Customer relationships	19	years		15,129	$	-5,495		15,037	$	-4,772
		Software	5	years		5,040		-2,832		4,271		-2,405
		Cable franchise renewal costs and contractual operating rights	10	years		1,418		-792		1,360		-745
		Patents and other technology rights	8	years		373		-330		361		-307
		Other agreements and rights	20	years		1,456		-721		1,433		-645
	Total				$	86,514	$	-10,170	$	85,567	$	-8,874
	Indefinite-Lived Intangible Assets
	Indefinite-lived intangible assets consist primarily of our cable franchise rights, as well as trade names and FCC licenses. Our cable franchise rights represent the values we attributed to agreements with state and local authorities that allow access to homes and businesses in cable service areas acquired in business combinations. We do not amortize our cable franchise rights because we have determined that they meet the definition of indefinite-lived intangible assets since there are no legal, regulatory, contractual, competitive, economic or other factors which limit the period over which these rights will contribute to our cash flows. We reassess this determination periodically or whenever events or substantive changes in circumstances occur. Costs we incur in negotiating and renewing cable franchise agreements are included in other intangible assets and are generally amortized on a straight-line basis over the term of the franchise agreement.
	We assess the recoverability of our cable franchise rights and other indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. Our three Cable Communications divisions represent the unit of account we use to test for impairment for our cable franchise rights. We evaluate the unit of account used to test for impairment of our cable franchise rights and other indefinite-lived intangible assets periodically or whenever events or substantive changes in circumstances occur to ensure impairment testing is performed at an appropriate level. The assessment of recoverability may first consider qualitative factors to determine whether it is more likely than not that the fair value of an indefinite-lived intangible asset is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. When performing a quantitative assessment, we estimate the fair value of our cable franchise rights and other indefinite-lived intangible assets primarily based on a discounted cash flow analysis that involves significant judgment. When analyzing the fair values indicated under the discounted cash flow models, we also consider multiples of operating income before depreciation and amortization generated by the underlying assets, current market transactions, and profitability information. If the fair value of our cable franchise rights or other indefinite-lived intangible assets were less than the carrying amount, we would recognize an impairment charge for the difference between the estimated fair value and the carrying value of the assets. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any material impairment charges in any of the periods presented.
	Finite-Lived Intangible Assets
	Estimated Amortization Expense of Finite-Lived Intangible Assets
	(in millions)
	2015	$	1,619
	2016	$	1,457
	2017	$	1,296
	2018	$	1,053
	2019	$	842
	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, software, cable franchise renewal costs, contractual operating rights, and intellectual property rights. Our finite-lived intangible assets are amortized primarily on a straight-line basis over their estimated useful life or the term of the associated agreement.
	We capitalize direct development costs associated with internal-use software, including external direct costs of material and services and payroll costs for employees devoting time to these software projects. We also capitalize costs associated with the purchase of software licenses. We include these costs in other intangible assets and amortize them on a straight-line basis over a period not to exceed five years. We expense maintenance and training costs, as well as costs incurred during the preliminary stage of a project, as they are incurred. We capitalize initial operating system software costs and amortize them over the life of the associated hardware.
	We evaluate the recoverability of our finite-lived intangible assets whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
NBCUniversal Media, LLC [Member]
Goodwill and Intangible Assets	Note 9: Goodwill and Intangible Assets
	Goodwill
	(in millions)			Cable Networks		Broadcast Television		Filmed Entertainment		Theme Parks		Total
	Balance, December 31, 2012		$	13,026	$	761	$	1	$	982	$	14,770
	Acquisitions			39		3		-		-		42
	Adjustments			65		5		-		-		70
	Balance, December 31, 2013			13,130		769		1		982		14,882
	Acquisitions			20		-		15		-		35
	Adjustments(a)			-202		-2		195		-		-9
	Balance, December 31, 2014		$	12,948	$	767	$	211	$	982	$	14,908
	(a) Adjustments to goodwill in 2014 were primarily related to the reclassification of Fandango, our movie ticketing and entertainment business, from our Cable Networks segment to our Filmed Entertainment segment.
	We assess the recoverability of our goodwill annually, or more frequently whenever events or substantive changes in circumstances indicate that the carrying amount of a reporting unit may exceed its fair value. We test goodwill for impairment at the reporting unit level. To determine our reporting units, we evaluate the components one level below the segment level and we aggregate the components if they have similar economic characteristics. As a result of this assessment, our reporting units are the same as our four reportable segments. We evaluate the determination of our reporting units used to test for impairment periodically or whenever events or substantive changes in circumstances occur. The assessment of recoverability may first consider qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. The quantitative assessment considers if the carrying amount of a reporting unit exceeds its fair value, in which case an impairment charge is recorded to the extent the carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
	Intangible Assets
						2014				2013
	December 31 (in millions)		Weighted-Average Original Useful Life as of December 31, 2014			Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
	Finite-Lived Intangible Assets:
		Customer relationships	19 years		$	13,093	$	-3,636	$	13,086	$	-2,982
		Software	5 years			657		-329		522		-240
		Other	21 years			1,556		-864		1,511		-781
	Indefinite-Lived Intangible Assets:
		Trade names	N/A			3,059				3,089
		FCC licenses	N/A			651				652
	Total				$	19,016	$	-4,829	$	18,860	$	-4,003
	Indefinite-Lived Intangible Assets
	Indefinite-lived intangible assets consist of trade names and FCC licenses. We assess the recoverability of our indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. We evaluate the unit of account used to test for impairment of our indefinite-lived intangible assets periodically or whenever events or substantive changes in circumstances occur to ensure impairment testing is performed at an appropriate level. The assessment of recoverability may first consider qualitative factors to determine whether it is more likely than not that the fair value of an indefinite-lived intangible asset is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. When performing a quantitative assessment, we estimate the fair value of our indefinite-lived intangible assets primarily based on a discounted cash flow analysis that involves significant judgment. When analyzing the fair values indicated under the discounted cash flow models, we also consider multiples of operating income before depreciation and amortization generated by the underlying assets, current market transactions, and profitability information. If the fair value of our indefinite-lived intangible assets were less than the carrying amount, we would recognize an impairment charge for the difference between the estimated fair value and the carrying value of the assets. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any material impairment charges in any of the periods presented.
	Finite-Lived Intangible Assets
	Estimated Amortization Expense of Finite-Lived Intangible Assets
	(in millions)
	2015	$	777
	2016	$	748
	2017	$	747
	2018	$	743
	2019	$	740
	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, intellectual property rights and software. Our finite-lived intangible assets are amortized primarily on a straight-line basis over their estimated useful life or the term of the associated agreement.
	We capitalize direct development costs associated with internal-use software, including external direct costs of material and services and payroll costs for employees devoting time to these software projects. We also capitalize costs associated with the purchase of software licenses. We include these costs in intangible assets and amortize them on a straight-line basis over a period not to exceed five years. We expense maintenance and training costs, as well as costs incurred during the preliminary stage of a project, as they are incurred. We capitalize initial operating system software costs and amortize them over the life of the associated hardware.
	We evaluate the recoverability of our finite-lived intangible assets whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2014
Long-Term Debt	Note 10: Long-Term Debt
	Long-Term Debt Outstanding
	December 31 (in millions)	Weighted-Average Interest Rate as of December 31, 2014			2014		2013
	Commercial paper	0.373	%	$	845	$	1,350
	Revolving bank credit facilities	—	%		-		1,250
	Senior notes with maturities of 5 years or less	4.642	%		15,334		15,080
	Senior notes with maturities between 5 and 10 years	4.822	%		10,527		11,533
	Senior notes with maturities greater than 10 years(a)	5.737	%		20,937		18,010
	Other, including capital lease obligations	—			591		624
	Total debt	4.95	%(b)		48,234		47,847
	Less: Current portion				4,217		3,280
	Long-term debt			$	44,017	$	44,567
	(a) The December 31, 2014 and 2013 amounts include £625 million of 5.50% notes due 2029 which translated to $974 million and $1 billion, respectively, using the exchange rates as of these dates.
	(b) Includes the effects of our derivative financial instruments.
	As of December 31, 2014 and 2013, our debt had an estimated fair value of $55.3 billion and $51.8 billion, respectively. The estimated fair value of our publicly traded debt is primarily based on Level 1 inputs that use quoted market values for the debt. The estimated fair value of debt for which there are no quoted market prices is based on Level 2 inputs that use interest rates available to us for debt with similar terms and remaining maturities. See Note 20 for additional information on our cross-guarantee structure.
	Debt Maturities
	(in millions)	Weighted-Average Interest Rate as of December 31, 2014
	2015	4.99	%		$	4,217
	2016	4.158	%		$	3,530
	2017	6.973	%		$	2,558
	2018	4.124	%		$	4,117
	2019	3.159	%		$	2,205
	Thereafter	5.425	%		$	31,607
	2014 Debt Borrowings
	Year ended December 31, 2014 (in millions)
	Comcast 3.600% senior notes due 2024	$	1,200
	Comcast 3.375% senior notes due 2025		1,000
	Comcast 4.200% senior notes due 2034		1,000
	Comcast 4.750% senior notes due 2044		1,000
	Total	$	4,200
	2014 Debt Repayments
	Year ended December 31, 2014 (in millions)
	NBCUniversal Enterprise revolving credit facility	$	1,250
	Comcast 5.300% senior notes due 2014		1,000
	NBCUniversal 2.100% senior notes due 2014		900
	Other		25
	Total	$	3,175
	Debt Instruments
	Revolving Credit Facilities
	As of December 31, 2014, Comcast and Comcast Cable Communications, LLC had a $6.25 billion revolving credit facility due June 2017 with a syndicate of banks. The interest rate on this facility consists of a base rate plus a borrowing margin that is determined based on our credit rating. As of December 31, 2014, the borrowing margin for London Interbank Offered Rate (“LIBOR”) based borrowings was 1.00%. This revolving credit facility requires that we maintain certain financial ratios based on our debt and our operating income before depreciation and amortization, as defined in the credit facility. We were in compliance with all financial covenants for all periods presented.
	As of December 31, 2014, NBCUniversal Enterprise had a $1.35 billion revolving credit facility due March 2018 with a syndicate of banks. The interest rate on this facility consists of a base rate plus a borrowing margin that is determined based on our credit rating. As of December 31, 2014, the borrowing margin for LIBOR-based borrowings was 1.00%.
	As of December 31, 2014, amounts available under our consolidated credit facilities, net of amounts outstanding under our commercial paper programs and outstanding letters of credit, totaled $6.5 billion, which included $505 million available under NBCUniversal Enterprise’s revolving credit facility.
	Commercial Paper Programs
	Our commercial paper programs provide a lower-cost source of borrowing to fund our short-term working capital requirements. The Comcast commercial paper program is supported by the Comcast and Comcast Cable Communications, LLC $6.25 billion revolving credit facility due June 2017. In February 2014, NBCUniversal Enterprise entered into a commercial paper program. The maximum borrowing capacity under this commercial paper program is $1.35 billion, and it is supported by NBCUniversal Enterprise’s revolving credit facility.
	Letters of Credit
	As of December 31, 2014, we and certain of our subsidiaries had unused irrevocable standby letters of credit totaling $473 million to cover potential fundings under various agreements.
NBCUniversal Media, LLC [Member]
Long-Term Debt	Note 10: Long-Term Debt
	Long-Term Debt Outstanding
	December 31 (in millions)	Weighted-Average Interest Rate as of December 31, 2014		2014			2013
	Senior notes with maturities of 5 years or less	3.254	%	$	2,005	$	2,917
	Senior notes with maturities between 5 and 10 years	4.389	%		4,996		4,996
	Senior notes with maturities greater than 10 years	5.614	%		3,204		3,205
	Other, including capital lease obligations	—			44		47
	Total debt	4.46	%(a)		10,249		11,165
	Less: Current portion				1,023		906
	Long-term debt			$	9,226	$	10,259
	(a) Includes the effects of our derivative financial instruments.
	As of December 31, 2014 and 2013, our debt had an estimated fair value of $11.5 billion and $11.7 billion, respectively. The estimated fair value of our publicly traded debt is primarily based on Level 1 inputs that use quoted market values for the debt. The estimated fair value of debt for which there are no quoted market prices is based on Level 2 inputs that use interest rates available to us for debt with similar terms and remaining maturities.
	Debt Maturities
	(in millions)	Weighted-Average Interest Rate as of December 31, 2014
	2015	3.633	%		$	1,023
	2016	2.894	%		$	1,008
	2017	6.296	%		$	2
	2018	6.307	%		$	2
	2019	6.329	%		$	2
	Thereafter	4.871	%		$	8,212
	Debt Repayments
	In April 2014, we repaid at maturity $900 million aggregate principal amount of 2.10% senior notes due 2014.
	Cross-Guarantee Structure
	In 2013, we, Comcast and certain of Comcast’s 100% owned cable holding company subsidiaries (the “cable guarantors”) entered into a series of agreements and supplemental indentures to include us as a part of Comcast’s existing cross-guarantee structure. As members of the cross-guarantee structure, Comcast and the cable guarantors fully and unconditionally guarantee our public debt securities, and we fully and unconditionally guarantee all of Comcast’s and the cable guarantors’ public debt securities. As of December 31, 2014, we guaranteed $32.6 billion of outstanding debt securities of Comcast and the cable guarantors. We also fully and unconditionally guarantee the $6.25 billion Comcast revolving credit facility due June 2017, of which no amounts were outstanding as of December 31, 2014.
	We do not, however, guarantee the obligations of NBCUniversal Enterprise with respect to its $4 billion aggregate principal amount of senior notes, $1.35 billion revolving credit facility and associated commercial paper program, or $725 million liquidation preference of Series A cumulative preferred stock.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements	Note 11: Fair Value Measurements
	The accounting guidance related to financial assets and financial liabilities (“financial instruments”) establishes a hierarchy that prioritizes fair value measurements based on the types of inputs used for the various valuation techniques (market approach, income approach and cost approach). The levels of the hierarchy are described below.
	Level 1: Consists of financial instruments whose values are based on quoted market prices for identical financial instruments in an active market.
	Level 2: Consists of financial instruments that are valued using models or other valuation methodologies. These models use inputs that are observable either directly or indirectly. Level 2 inputs include (1) quoted prices for similar assets or liabilities in active markets, (2) quoted prices for identical or similar assets or liabilities in markets that are not active, (3) pricing models whose inputs are observable for substantially the full term of the financial instrument and (4) pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument.
	Level 3: Consists of financial instruments whose values are determined using pricing models that use significant inputs that are primarily unobservable, discounted cash flow methodologies or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.
	Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial instruments and their classification within the fair value hierarchy. Financial instruments are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. There have been no changes in the classification of any financial instruments within the fair value hierarchy in the periods presented. Our financial instruments that are accounted for at fair value on a recurring basis are presented in the table below.
	Recurring Fair Value Measures
			Fair Value as of December 31, 2014								Fair Value as of December 31, 2013
	(in millions)		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
	Assets
	Trading securities	$	523	$	-	$	-	$	523	$	3,956	$	-	$	-	$	3,956
	Available-for-sale securities		1		121		10		132		260		118		11		389
	Interest rate swap agreements		-		84		-		84		-		110		-		110
	Other		-		64		7		71		-		80		1		81
	Total	$	524	$	269	$	17	$	810	$	4,216	$	308	$	12	$	4,536
	Liabilities
	Derivative component of prepaid forward sale agreements and indexed debt instruments	$	-	$	361	$	-	$	361	$	-	$	2,816	$	-	$	2,816
	Contractual obligations		-		-		883		883		-		-		747		747
	Contingent consideration		-		-		644		644		-		-		684		684
	Other		-		8		-		8		-		16		-		16
	Total	$	-	$	369	$	1,527	$	1,896	$	-	$	2,832	$	1,431	$	4,263
	Contractual Obligations and Contingent Consideration
	The estimated fair values of the contractual obligations and contingent consideration in the table above are primarily based on certain expected future discounted cash flows, the determination of which involves the use of significant unobservable inputs. The most significant unobservable inputs we use include our estimates of the future revenue we expect to generate from certain NBCUniversal businesses, which are related to our contractual obligations, and future net tax benefits that will affect payments to GE, which are related to our contingent consideration. The discount rates used in the measurements of fair value as of December 31, 2014 were between 5% and 13% and are based on the underlying risk associated with our estimate of future revenue, the terms of the respective contracts and the uncertainty in the timing of our payments to GE. The fair value adjustments to contractual obligations and contingent consideration are sensitive to the assumptions related to future revenue and tax benefits, respectively, as well as to current interest rates, and therefore the adjustments are recorded to other income (expense), net in our consolidated statement of income.
	Changes in Contractual Obligations and Contingent Consideration
	(in millions)		Contractual Obligations		Contingent Consideration
	Balance, December 31, 2013	$	747	$	684
	Fair value adjustments		208		31
	Payments		-72		-71
	Balance, December 31, 2014	$	883	$	644
	Nonrecurring Fair Value Measures
	We have assets and liabilities that are required to be recorded at fair value on a nonrecurring basis when certain circumstances occur. In the case of film, television or stage play production costs, upon the occurrence of an event or change in circumstance that may indicate that the fair value of a production is less than its unamortized costs, we determine the fair value of the production and record an adjustment for the amount by which the unamortized capitalized costs exceed the production’s fair value. The estimated fair value of a production is based on Level 3 inputs that primarily use an analysis of future expected cash flows. Adjustments to capitalized film and stage play production costs of $26 million, $167 million and $161 million were recorded in 2014, 2013 and 2012, respectively.
NBCUniversal Media, LLC [Member]
Fair Value Measurements	Note 11: Fair Value Measurements
	The accounting guidance related to financial assets and financial liabilities (“financial instruments”) establishes a hierarchy that prioritizes fair value measurements based on the types of inputs used for the various valuation techniques (market approach, income approach and cost approach). Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial instruments and their classification within the fair value hierarchy.
	Our financial instruments that are accounted for at fair value on a recurring basis were not material for all periods presented, except for liabilities associated with our contractual obligations. The fair values of the contractual obligations in the table below are primarily based on certain expected future discounted cash flows, the determination of which involves the use of significant unobservable inputs. As the inputs used are not quoted market prices or observable inputs, we classify these contractual obligations as Level 3 financial instruments.
	The most significant unobservable inputs we use are our estimates of the future revenue we expect to generate from certain of our businesses. The discount rates used in the measurements of fair value as of December 31, 2014 were between 12% and 13% and are based on the underlying risk associated with our estimate of future revenue and the terms of the respective contracts. The fair value adjustments to contractual obligations are sensitive to the assumptions related to future revenue, as well as to current interest rates, and therefore the adjustments are recorded to other income (expense), net in our consolidated statement of income.
	Changes in Contractual Obligations
	(in millions)
	Balance, December 31, 2013	$	747
	Fair value adjustments		208
	Payments		-72
	Balance, December 31, 2014	$	883
	Nonrecurring Fair Value Measures
	We have assets and liabilities that are required to be recorded at fair value on a nonrecurring basis when certain circumstances occur. In the case of film, television or stage play production costs, upon the occurrence of an event or change in circumstance that may indicate that the fair value of a production is less than its unamortized costs, we determine the fair value of the production and record an adjustment for the amount by which the unamortized capitalized costs exceed the production’s fair value. The estimated fair value of a production is based on Level 3 inputs that primarily use an analysis of future expected cash flows. Adjustments to capitalized film and stage play production costs of $26 million, $167 million and $161 million were recorded in 2014, 2013 and 2012, respectively.

Pension_Plans_and_Postretireme

Pension Plans and Postretirement Benefits	12 Months Ended
	Dec. 31, 2014
Postretirement, Pension and Other Employee Benefit Plans	Note 12: Postretirement, Pension and Other Employee Benefit Plans
	The table below provides condensed information on our postretirement and pension benefit plans.
				2014					2013						2012
	Year ended December 31 (in millions)			Postretirement Benefits		Pension Benefits			Postretirement Benefits			Pension Benefits			Postretirement Benefits			Pension Benefits
	Benefit obligation		$	837		$	581		$	633		$	498		$	703		$	805
	Fair value of plan assets(a)			-			242			-			220			-			403
	Plan funded status and recorded
		benefit obligation		-837			-339			-633			-278			-703			-402
	Portion of benefit obligation not
		yet recognized in benefits expense		46			53			-110			-3			17			151
	Benefits expense(b)			59			14			65			12			60			163
	Discount rate			4.25	%	3.75-4.25		%		5.00-5.25	%	4.50-5.25		%		4.25	%	3.25-4.25		%
	Expected return on plan assets			N/A			5	%		N/A			5	%		N/A			5	%
	(a) The fair value of the plan assets are primarily based on Level 1 inputs that use quoted market prices for identical financial instruments in an active market.
	(b) We did not recognize service costs related to our pension plans in 2014 and 2013 as the plans were frozen. The 2012 amount included service costs related to our pension benefits of $139 million.
	Postretirement Benefit Plans
	We sponsor various benefit plans that provide postretirement benefits to eligible employees based on years of service. The Comcast Postretirement Healthcare Stipend Program (the “stipend plan”) provides an annual stipend for reimbursement of healthcare costs to each eligible employee based on years of service. Under the stipend plan, we are not exposed to the increasing costs of healthcare because the benefits are fixed at a predetermined amount.
	NBCUniversal’s postretirement medical and life insurance plans provide continuous coverage to employees eligible to receive such benefits. A small number of eligible employees also participate in legacy plans of acquired companies.
	All of our postretirement benefit plans are unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for our postretirement benefit plans is determined using certain assumptions, including the discount rate.
	Pension Plans
	NBCUniversal
	NBCUniversal sponsors various qualified and nonqualified defined benefit plans for domestic employees for which future benefits have been frozen. We ceased to recognize service costs associated with these defined benefit plans following the date on which future benefits were frozen. The expense we recognize for our defined benefit plans is determined using certain assumptions, including the discount rate and the expected long-term rate of return on plan assets. We recognize the funded or unfunded status of our defined benefit plans as an asset or liability in our consolidated balance sheet and recognize changes in the funded status in the year in which the changes occur through accumulated other comprehensive income (loss). In addition to the defined benefit plans it sponsors, NBCUniversal is also obligated to reimburse GE for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of the NBCUniversal transaction in 2011.
	In October 2013, we provided notice to the plan participants of the qualified pension plan of our intent to terminate the plan effective December 31, 2013. On June 27, 2014, we filed a Standard Termination Notice with the Pension Benefit Guaranty Corporation (“PBGC”) and on August 26, 2014, the related PBGC review concluded with no objections. We filed for Internal Revenue Service (“IRS”) approval on May 23, 2014 and expect to fully fund and settle the plan within 120 days of receipt of approval. We currently anticipate the contributions required from us to fully fund and settle the plan to be $16 million.
	Other
	In August 2013, we settled all of our obligations related to the termination in February 2012 of the qualified pension plan that provided benefits to former employees of a company we acquired as part of the AT&T Broadband transaction in 2002. In connection with this final settlement, we fully funded the plan with additional contributions of $55 million and recorded an expense of $74 million in other operating and administrative expenses, which was previously recorded in accumulated other comprehensive income (loss).
	Other Employee Benefits
	Deferred Compensation Plans
	We maintain unfunded, nonqualified deferred compensation plans for certain members of management and nonemployee directors (each, a “participant”). The amount of compensation deferred by each participant is based on participant elections. Participant accounts, except for those in the NBCUniversal plan, are credited with income primarily based on a fixed annual rate. Participants in the NBCUniversal plan designate one or more valuation funds, independently established funds or indices that are used to determine the amount of income or loss to be credited or debited to the participant’s account. Participants are eligible to receive distributions of the amounts credited to their account based on elected deferral periods that are consistent with the plans and applicable tax law.
	The table below presents the benefit obligation and interest expense for our deferred compensation plans.
	Year ended December 31 (in millions)		2014		2013		2012
	Benefit obligation	$	1,774	$	1,434	$	1,247
	Interest expense	$	149	$	128	$	107
	We have purchased life insurance policies to recover a portion of the future payments related to our deferred compensation plans. As of December 31, 2014 and 2013, the cash surrender value of these policies, which is recorded to other noncurrent assets, was $628 million and $565 million, respectively.
	Retirement Investment Plans
	We sponsor several 401(k) defined contribution retirement plans that allow eligible employees to contribute a portion of their compensation through payroll deductions in accordance with specified plan guidelines. We make contributions to the plans that include matching a percentage of the employees’ contributions up to certain limits. In 2014, 2013 and 2012, expenses related to these plans totaled $379 million, $324 million and $246 million, respectively.
	Split-Dollar Life Insurance Agreements
	We have collateral assignment split-dollar life insurance agreements with select key current and former employees that require us to incur certain insurance-related costs. Under some of these agreements, our obligation to provide benefits to the employees extends beyond retirement.
	The table below presents the benefit obligation and expenses related to our split-dollar life insurance agreements.
	Year ended December 31 (in millions)		2014		2013		2012
	Benefit obligation	$	217	$	212	$	202
	Other operating and administrative expenses	$	52	$	50	$	58
	Multiemployer Benefit Plans
	We participate in various multiemployer benefit plans, including pension and postretirement benefit plans, that cover some of our employees and temporary employees who are represented by labor unions. We also participate in other multiemployer benefit plans that provide health and welfare and retirement savings benefits to active and retired participants. We make periodic contributions to these plans in accordance with the terms of applicable collective bargaining agreements and laws but do not sponsor or administer these plans. We do not participate in any multiemployer benefit plans for which we consider our contributions to be individually significant, and the largest plans in which we participate are funded at a level of 80% or greater.
	In 2014, 2013 and 2012, the total contributions we made to multiemployer pension plans were $58 million, $59 million and $40 million, respectively. In 2014, 2013 and 2012, the total contributions we made to multiemployer postretirement and other benefit plans were $125 million, $98 million and $114 million, respectively.
	If we cease to be obligated to make contributions or were to otherwise withdraw from participation in any of these plans, applicable law would require us to fund our allocable share of the unfunded vested benefits, which is known as a withdrawal liability. In addition, actions taken by other participating employers may lead to adverse changes in the financial condition of one of these plans, which could result in an increase in our withdrawal liability.
	Severance Benefits
	We provide severance benefits to certain former employees. A liability is recorded for benefits provided when payment is probable, the amount is reasonably estimable, and the obligation relates to rights that have vested or accumulated. In 2014, 2013 and 2012, we recorded severance costs of $152 million, $160 million and $155 million, respectively.
NBCUniversal Media, LLC [Member]
Postretirement, Pension and Other Employee Benefit Plans	Note 12: Postretirement, Pension and Other Employee Benefit Plans
	The table below provides condensed information on our postretirement and pension benefit plans.
			2014						2013						2012
	Year ended December 31 (in millions)		Postretirement Benefits			Pension Benefits			Postretirement Benefits			Pension Benefits			Postretirement Benefits			Pension Benefits
	Benefit obligation		$	209		$	581		$	158		$	498		$	177		$	546
	Fair value of plan assets(a)			-			242			-			220			-			217
	Plan funded status and recorded
		benefit obligation		-209			-339			-158			-278			-177			-329
	Portion of benefit obligation not yet
		recognized in benefit expense		-3			53			-44			-3			-11			53
	Benefits expense(b)			12			14			14			12			15			142
	Discount rate			4.25	%		3.75-4.25	%		5.25	%		4.50-5.25	%		4.25	%		3.75-4.25	%
	Expected return on plan assets			N/A			5	%		N/A			5	%		N/A			5	%
	(a) The fair value of the plan assets are primarily based on Level 1 inputs that use quoted market prices for identical financial instruments in an active market.
	(b) We did not recognize service costs related to our pension plans in 2014 and 2013 as the plans were frozen. The 2012 amount included service costs related to our pension benefits of $134 million.
	Postretirement Benefit Plans
	We have postretirement medical and life insurance plans that provide continuous coverage to employees eligible to receive such benefits and give credit for length of service provided before the close of the joint venture transaction.
	Substantially all of the employees that were contributed by Comcast as part of the joint venture transaction participate in a postretirement healthcare stipend program (the “stipend plan”). The stipend plan provides an annual stipend for reimbursement of healthcare costs to each eligible employee based on years of service. Under the stipend plan, we are not exposed to the increasing costs of healthcare because the benefits are fixed at a predetermined amount.
	All of our postretirement benefit plans are unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for our postretirement benefit plans is determined using certain assumptions, including the discount rate.
	Pension Plans
	We sponsor various qualified and nonqualified defined benefit plans for domestic employees for which future benefits have been frozen. We ceased to recognize service costs associated with these defined benefit plans following the date on which future benefits were frozen. The expense we recognize for our defined benefit plans is determined using certain assumptions, including the discount rate and the expected long-term rate of return on plan assets. We recognize the funded or unfunded status of our defined benefit plans as an asset or liability in our consolidated balance sheet and recognize changes in the funded status in the year in which the changes occur through accumulated other comprehensive income (loss). In addition to the defined benefit plans we sponsor, we are also obligated to reimburse GE for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of the joint venture transaction.
	In October 2013, we provided notice to the plan participants of the qualified pension plan of our intent to terminate the plan effective December 31, 2013. On June 27, 2014, we filed a Standard Termination Notice with the Pension Benefit Guaranty Corporation (“PBGC”) and on August 26, 2014, the related PBGC review concluded with no objections. We filed for Internal Revenue Service (“IRS”) approval on May 23, 2014 and expect to fully fund and settle the plan within 120 days of receipt of approval. We currently anticipate the contributions required from us to fully fund and settle the plan to be $16 million.
	Our consolidated balance sheet also includes the assets and liabilities of certain legacy pension plans, as well as the assets and liabilities for pension plans of certain foreign subsidiaries. As of December 31, 2014 and 2013, the benefit obligations associated with these plans exceeded the fair value of the plan assets by $51 million and $43 million, respectively.
	Other Employee Benefits
	Deferred Compensation Plans
	We maintain unfunded, nonqualified deferred compensation plans for certain members of management and nonemployee directors (each, a “participant”). The amount of compensation deferred by each participant is based on participant elections. Participants in the plan designate one or more valuation funds, independently established funds or indices that are used to determine the amount of income or loss to be credited or debited to the participant’s account.
	Additionally, certain of our employees participate in Comcast’s unfunded, nonqualified deferred compensation plan. The amount of compensation deferred by each participant is based on participant elections. Participant accounts are credited with income primarily based on a fixed annual rate.
	In the case of both deferred compensation plans, participants are eligible to receive distributions of the amounts credited to their account based on elected deferral periods that are consistent with the plans and applicable tax law.
	The table below presents the benefit obligation and interest expense for our deferred compensation plans.
	Year ended December 31 (in millions)		2014		2013		2012
	Benefit obligation	$	349	$	250	$	163
	Interest expense	$	24	$	18	$	11
	Retirement Investment Plans
	We sponsor several 401(k) defined contribution retirement plans that allow eligible employees to contribute a portion of their compensation through payroll deductions in accordance with specified plan guidelines. We make contributions to the plans that include matching a percentage of the employees’ contributions up to certain limits. In 2014, 2013 and 2012, expenses related to these plans totaled $165 million, $152 million and $85 million, respectively.
	Multiemployer Benefit Plans
	We participate in various multiemployer benefit plans, including pension and postretirement benefit plans, that cover some of our employees and temporary employees who are represented by labor unions. We also participate in other multiemployer benefit plans that provide health and welfare and retirement savings benefits to active and retired participants. We make periodic contributions to these plans in accordance with the terms of applicable collective bargaining agreements and laws but do not sponsor or administer these plans. We do not participate in any multiemployer benefit plans for which we consider our contributions to be individually significant, and the largest plans in which we participate are funded at a level of 80% or greater.
	In 2014, 2013 and 2012, the total contributions we made to multiemployer pension plans were $58 million, $59 million and $40 million, respectively. In 2014, 2013 and 2012, the total contributions we made to multiemployer postretirement and other benefit plans were $125 million, $98 million and $114 million, respectively.
	If we cease to be obligated to make contributions or were to otherwise withdraw from participation in any of these plans, applicable law would require us to fund our allocable share of the unfunded vested benefits, which is known as a withdrawal liability. In addition, actions taken by other participating employers may lead to adverse changes in the financial condition of one of these plans, which could result in an increase in our withdrawal liability.
	Severance Benefits
	We provide severance benefits to certain former employees. A liability is recorded for benefits provided when payment is probable, the amount is reasonably estimable, and the obligation relates to rights that have vested or accumulated. In 2014, 2013 and 2012, we recorded severance costs of $113 million, $116 million and $90 million, respectively.

Equity

Equity	12 Months Ended
	Dec. 31, 2014
Equity	Note 13: Equity
	Common Stock
	In the aggregate, holders of our Class A common stock have 66 2/3% of the voting power of our common stock and holders of our Class B common stock have 331/3% of the voting power of our common stock. Our Class A Special common stock is generally nonvoting. Each share of our Class B common stock is entitled to 15 votes. The number of votes held by each share of our Class A common stock depends on the number of shares of Class A and Class B common stock outstanding at any given time. The 331/3% aggregate voting power of our Class B common stock cannot be diluted by additional issuances of any other class of common stock. Our Class B common stock is convertible, share for share, into Class A or Class A Special common stock, subject to certain restrictions.
	Shares of Common Stock Outstanding
	(in millions)	A	A Special	B
	Balance, December 31, 2011	2,095	601	9
	Stock compensation plans	24	3	-
	Repurchases and retirements of common stock	-	-96	-
	Employee stock purchase plans	3	-	-
	Balance, December 31, 2012	2,122	508	9
	Stock compensation plans	14	-	-
	Repurchases and retirements of common stock	-	-49	-
	Employee stock purchase plans	2	-	-
	Balance, December 31, 2013	2,138	459	9
	Stock compensation plans	13	-	-
	Repurchases and retirements of common stock	-22	-59	-
	Employee stock purchase plans	2	-	-
	Balance, December 31, 2014	2,131	400	9
	Share Repurchases
	As of December 31, 2014, we had $3.25 billion of availability remaining under the $7.5 billion share repurchase authorization approved by our Board of Directors in 2014.
	In February 2015, our Board of Directors increased our share repurchase program authorization to $10 billion, which does not have an expiration date. Under this authorization, we may repurchase shares in the open market or in private transactions.
	Share Repurchases
	Year ended December 31 (in millions)		2014		2013		2012
	Cash consideration	$	4,251	$	2,000	$	3,000
	Shares repurchased		81		49		96
	Accumulated Other Comprehensive Income (Loss)
	December 31 (in millions)			2014		2013
	Unrealized gains (losses) on marketable securities		$	1	$	67
	Deferred gains (losses) on cash flow hedges			-4		-45
	Unrecognized gains (losses) on employee benefit obligations			-68		71
	Cumulative translation adjustments			-75		-37
	Accumulated other comprehensive income (loss), net of deferred taxes		$	-146	$	56

ShareBased_Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2014
Share-Based Compensation	Note 14: Share-Based Compensation
	The tables below provide condensed information on our share-based compensation.
	Recognized Share-Based Compensation Expense
	Year ended December 31 (in millions)		2014		2013		2012
	Stock options	$	160	$	139	$	131
	Restricted share units		231		175		154
	Employee stock purchase plans		23		20		16
	Total	$	414	$	334	$	301
	As of December 31, 2014, we had unrecognized pretax compensation expense of $321 million related to nonvested stock options and unrecognized pretax compensation expense of $505 million related to nonvested RSUs that will be recognized over a weighted-average period of approximately 1.8 years and 1.7 years, respectively. In 2014, 2013 and 2012, we recorded an increase to additional paid-in capital of $299 million, $244 million and $164 million, respectively, which was the result of a tax benefit associated with our share-based compensation plans.
	Stock Options and Restricted Share Units
	As of December 31, 2014, unless otherwise stated (in millions, except per share data)			Stock Options		RSUs
	Awards granted during 2014			16		8
	Weighted-average exercise price of awards granted during 2014		$	50.03
	Stock options outstanding and nonvested RSUs			98		24
	Weighted-average exercise price of stock options outstanding		$	30.29
	Weighted-average fair value at grant date of nonvested RSUs				$	34.11
	As of December 31, 2014, substantially all of our stock options outstanding were net settled stock options. Net settled stock options, as opposed to stock options exercised with a cash payment, result in fewer shares being issued and no cash proceeds being received by us when the options are exercised. Our share-based compensation primarily consists of awards of stock options and RSUs to certain employees and directors as part of our approach to long-term incentive compensation. Awards generally vest over a period of 5 years and in the case of stock options, have a 10 year term. Additionally, through our employee stock purchase plans, employees are able to purchase shares of Comcast Class A common stock at a discount through payroll deductions.
	The cost associated with our share-based compensation is based on an award’s estimated fair value at the date of grant and is recognized over the period in which any related services are provided. We use the Black-Scholes option pricing model to estimate the fair value of stock option awards. RSUs are valued based on the closing price of our Class A common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period. The table below presents the weighted-average fair value on the date of grant of RSUs and Class A common stock options awarded under our various plans and the related weighted-average valuation assumptions.
	Year ended December 31			2014			2013			2012
	RSUs fair value		$	47.91		$	38.28		$	27.8
	Stock options fair value		$	11.11		$	8.8		$	7.38
	Stock Option Valuation Assumptions:
		Dividend yield		1.8	%		1.9	%		2.2	%
		Expected volatility		24	%		25	%		29	%
		Risk-free interest rate		2.2	%		1.3	%		1.7	%
		Expected option life (in years)		6.5			7			7
NBCUniversal Media, LLC [Member]
Share-Based Compensation	Note 13: Share-Based Compensation
	The tables below provide condensed information on our share-based compensation.
	Recognized Share-Based Compensation Expense
	Year ended December 31 (in millions)	2014		2013		2012
	Stock options	$	16	$	15	$	15
	Restricted share units		69		42		28
	Employee stock purchase plans		6		5		4
	Total	$	91	$	62	$	47
	As of December 31, 2014, we had unrecognized pretax compensation expense of $25 million related to nonvested Comcast stock options and unrecognized pretax compensation expense of $124 million related to nonvested Comcast restricted share units (“RSUs”) that will be recognized over a weighted-average period of approximately 2.1 years and 1.6 years, respectively.
	Comcast maintains share-based compensation plans that primarily consist of awards of stock options and RSUs to certain employees and directors as part of its approach to long-term incentive compensation. Awards generally vest over a period of 5 years and in the case of stock options, have a 10 year term. Additionally, through its employee stock purchase plans, employees are able to purchase shares of Comcast Class A common stock at a discount through payroll deductions. Certain of our employees participate in these plans and the expense associated with their participation is settled in cash with Comcast.
	The cost associated with Comcast’s share-based compensation is based on an award’s estimated fair value at the date of grant and is recognized over the period in which any related services are provided. Comcast uses the Black-Scholes option pricing model to estimate the fair value of stock option awards. RSUs are valued based on the closing price of Comcast Class A common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period. The table below presents the weighted-average fair value on the date of grant of RSUs and Class A common stock options awarded under Comcast’s various plans to employees of NBCUniversal and the related weighted-average valuation assumptions.
	Year ended December 31			2014			2013			2012
	RSUs fair value		$	48.04		$	37.79		$	27.51
	Stock options fair value		$	11.09		$	8.86		$	7.42
	Stock Option Valuation Assumptions:
		Dividend yield		1.8	%		1.9	%		2.2	%
		Expected volatility		24	%		25.2	%		29	%
		Risk-free interest rate		2.2	%		1.3	%		1.7	%
		Expected option life (in years)		6.5			7			7

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes	Note 15: Income Taxes
	Components of Income Tax Expense
	Year ended December 31 (in millions)			2014		2013		2012
	Current Expense (Benefit):
		Federal	$	2,392	$	3,183	$	3,004
		State		174		581		432
		Foreign		142		200		169
				2,708		3,964		3,605
	Deferred Expense (Benefit):
		Federal		1,000		-76		160
		State		173		108		-40
		Foreign		-8		-16		19
				1,165		16		139
	Income tax expense		$	3,873	$	3,980	$	3,744
	Our income tax expense differs from the federal statutory amount because of the effect of the items detailed in the table below.
	Year ended December 31 (in millions)		2014		2013		2012
	Federal tax at statutory rate	$	4,363	$	3,890	$	4,063
	State income taxes, net of federal benefit		329		319		178
	Foreign income taxes, net of federal credit		-		15		92
	Nontaxable income attributable to noncontrolling interests		-62		-103		-620
	Adjustments to uncertain and effectively settled tax positions, net		-408		58		114
	Accrued interest on uncertain and effectively settled tax positions, net		-235		114		23
	Other		-114		-313		-106
	Income tax expense	$	3,873	$	3,980	$	3,744
	We base our provision for income taxes on our current period income, changes in our deferred income tax assets and liabilities, income tax rates, changes in estimates of our uncertain tax positions, and tax planning opportunities available in the jurisdictions in which we operate. We recognize deferred tax assets and liabilities when there are temporary differences between the financial reporting basis and tax basis of our assets and liabilities and for the expected benefits of using net operating loss carryforwards. When a change in the tax rate or tax law has an impact on deferred taxes, we apply the change based on the years in which the temporary differences are expected to reverse. We record the change in our consolidated financial statements in the period of enactment.
	Income tax consequences that arise in connection with a business combination include identifying the tax basis of assets and liabilities acquired and any contingencies associated with uncertain tax positions assumed or resulting from the business combination. Deferred tax assets and liabilities related to temporary differences of an acquired entity are recorded as of the date of the business combination and are based on our estimate of the ultimate tax basis that will be accepted by the various taxing authorities. We record liabilities for contingencies associated with prior tax returns filed by the acquired entity based on criteria set forth in the appropriate accounting guidance. We adjust the deferred tax accounts and the liabilities periodically to reflect any revised estimated tax basis and any estimated settlements with the various taxing authorities. The effects of these adjustments are recorded to income tax expense.
	From time to time, we engage in transactions in which the tax consequences may be subject to uncertainty. In these cases, we evaluate our tax positions using the recognition threshold and the measurement attribute in accordance with the accounting guidance related to uncertain tax positions. Examples of these transactions include business acquisitions and dispositions, including consideration paid or received in connection with these transactions, certain financing transactions, and the allocation of income among state and local taxing jurisdictions. Significant judgment is required in assessing and estimating the tax consequences of these transactions. We determine whether it is more likely than not that a tax position will be sustained on examination, including the resolution of any related appeals or litigation processes, based on the technical merits of the position. A tax position that meets the more-likely-than-not recognition threshold is measured to determine the amount of benefit to be recognized in our consolidated financial statements. We classify interest and penalties, if any, associated with our uncertain tax positions as a component of income tax expense.
	NBCUniversal
	For U.S. federal income tax purposes, NBCUniversal Holdings is treated as a partnership and NBCUniversal is disregarded as an entity separate from NBCUniversal Holdings. Accordingly, neither NBCUniversal Holdings nor NBCUniversal and its subsidiaries incur any material current or deferred domestic income taxes. Following the close of the NBCUniversal redemption transaction in March 2013, the taxable income of NBCUniversal Holdings and NBCUniversal is allocable entirely to us.
	We are indemnified by GE for any income tax liability attributable to the NBCUniversal contributed businesses for periods prior to the close of the NBCUniversal transaction and also for any income tax liability attributable to NBCUniversal Enterprise for periods prior to the date of the NBCUniversal redemption transaction. We have indemnified GE for any income tax liability attributable to the businesses we contributed to NBCUniversal for periods prior to the close of the NBCUniversal transaction.
	Current and deferred foreign income taxes are incurred by NBCUniversal’s foreign subsidiaries. In 2014, 2013 and 2012, NBCUniversal had foreign income before taxes of $385 million, $524 million and $434 million, respectively, on which foreign income tax expense was recorded. We recorded U.S. income tax expense on our allocable share of NBCUniversal’s income before domestic and foreign taxes, which was reduced by a U.S. tax credit equal to our allocable share of NBCUniversal’s foreign income tax expense.
	Components of Net Deferred Tax Liability
	December 31 (in millions)				2014		2013
	Deferred Tax Assets:
		Net operating loss carryforwards		$	448	$	495
		Differences between book and tax basis of long-term debt			116		117
		Nondeductible accruals and other			3,383		3,588
		Less: Valuation allowance			375		405
					3,572		3,795
	Deferred Tax Liabilities:
		Differences between book and tax basis of property and equipment and intangible assets			35,112		34,044
		Differences between book and tax basis of investments			186		473
		Differences between book and tax basis of indexed debt securities			534		610
		Differences between book and tax basis of foreign
			subsidiaries and undistributed foreign earnings		504		367
					36,336		35,494
	Net deferred tax liability			$	32,764	$	31,699
	Changes in net deferred income tax liabilities in 2014 that were not recorded as deferred income tax expense are primarily related to decreases of $127 million associated with items included in other comprehensive income (loss) and increases of $26 million related to acquisitions made in 2014. Our net deferred tax liability includes $23 billion related to cable franchise rights that will remain unchanged unless we recognize an impairment or dispose of a cable franchise. Following the NBCUniversal redemption transaction, we recognized an increase in our deferred tax liabilities of $1.6 billion primarily due to an increase in our financial reporting basis in the consolidated net assets of NBCUniversal Holdings in excess of the tax basis.
	Net deferred tax assets included in other current assets are primarily related to our current investments and current liabilities. As of December 31, 2014, we had federal net operating loss carryforwards of $127 million and various state net operating loss carryforwards that expire in periods through 2034. As of December 31, 2014, we also had foreign net operating loss carryforwards of $331 million that are related to the foreign operations of NBCUniversal, the majority of which expire in periods through 2024. The determination of the realization of the state and foreign net operating loss carryforwards is dependent on our subsidiaries’ taxable income or loss, apportionment percentages, and state and foreign laws that can change from year to year and impact the amount of such carryforwards. We recognize a valuation allowance if we determine it is more likely than not that some portion, or all, of a deferred tax asset will not be realized. As of December 31, 2014 and 2013, our valuation allowance was primarily related to state and foreign net operating loss carryforwards.
	Uncertain Tax Positions
	Our uncertain tax positions as of December 31, 2014 totaled $1.2 billion, which excludes the federal benefits on state tax positions that were recorded as deferred income taxes. Included in our uncertain tax positions was $243 million related to tax positions of NBCUniversal and NBCUniversal Enterprise for which we have been indemnified by GE. If we were to recognize the tax benefit for our uncertain tax positions in the future, $603 million would impact our effective tax rate and the remaining amount would increase our deferred income tax liability. The amount and timing of the recognition of any such tax benefit is dependent on the completion of examinations of our tax filings and the expiration of statutes of limitations. In September 2014, we reduced our accruals for uncertain tax positions and the related accrued interest on these tax positions. The reduction resulted in a decrease of $724 million in income tax expense, which excludes the benefits of uncertain tax positions for which we have been indemnified.
	Reconciliation of Unrecognized Tax Benefits
	(in millions)		2014		2013		2012
	Balance, January 1	$	1,701	$	1,573	$	1,435
	Additions based on tax positions related to the current year		63		90		154
	Additions based on tax positions related to prior years		111		201		79
	Additions from acquired subsidiaries		-		268		-
	Reductions for tax positions of prior years		-220		-141		-60
	Reductions due to expiration of statutes of limitations		-448		-3		-3
	Settlements with taxing authorities		-36		-287		-32
	Balance, December 31	$	1,171	$	1,701	$	1,573
	As of December 31, 2014 and 2013, our accrued interest associated with tax positions was $452 million and $780 million, respectively. As of December 31, 2014 and 2013, $44 million and $42 million, respectively, of these amounts were related to tax positions of NBCUniversal and NBCUniversal Enterprise for which we have been indemnified by GE.
	During 2014, the IRS completed its examination of our income tax returns for the year 2012. Various states are examining our tax returns through 2011. The tax years of our state tax returns currently under examination vary by state, with most of the periods relating to tax years 2000 and forward.
NBCUniversal Media, LLC [Member]
Income Taxes	Note 14: Income Taxes
	Components of Income Tax Expense
	Year ended December 31 (in millions)		2014		2013		2012
	Foreign
		Current income tax expense	$	33	$	77	$	69
		Deferred income tax expense		-8		-16		16
		Withholding tax expense		108		123		103
	U.S. domestic tax expense			10		22		9
	Income tax expense		$	143	$	206	$	197
	We are a limited liability company, and our company is disregarded for U.S. federal income tax purposes as an entity separate from NBCUniversal Holdings, a tax partnership. NBCUniversal and our subsidiaries are not expected to incur any significant current or deferred U.S. domestic income taxes. Our tax liability is comprised primarily of withholding tax on foreign licensing activity and income taxes on foreign earnings. As a result of our tax status, the deferred tax assets and liabilities included in our consolidated balance sheet at December 31, 2014 and 2013 were not material.
	In jurisdictions in which we are subject to income taxes, we base our provision for income taxes on our current period income, changes in our deferred income tax assets and liabilities, income tax rates, changes in estimates of our uncertain tax positions, and tax planning opportunities available in the jurisdictions in which we operate. We recognize deferred tax assets and liabilities when there are temporary differences between the financial reporting basis and tax basis of our assets and liabilities and for the expected benefits of using net operating loss carryforwards. When a change in the tax rate or tax law has an impact on deferred taxes, we apply the change based on the years in which the temporary differences are expected to reverse. We record the change in our consolidated financial statements in the period of enactment.
	We classify interest and penalties, if any, associated with our uncertain tax positions as a component of income tax expense.
	Uncertain Tax Positions
	We retain liabilities for uncertain tax positions where we are the tax filer of record. GE and Comcast have indemnified NBCUniversal Holdings and us with respect to our income tax obligations attributable to periods prior to the close of the joint venture transaction, including indemnification of uncertain tax positions for these periods. The liabilities for uncertain tax positions included in our consolidated balance sheet were not material as of December 31, 2014 and 2013.
	Various domestic and foreign taxing authorities are examining our tax returns through 2012. The majority of the periods under examination relate to tax years 2004 and forward.

Supplemental_Financial_Informa

Supplemental Financial Information	12 Months Ended
	Dec. 31, 2014
Supplemental Financial Information	Note 16: Supplemental Financial Information
	Receivables
	December 31 (in millions)		2014		2013
	Receivables, gross	$	6,885	$	6,972
	Less: Allowance for returns and customer incentives		359		375
	Less: Allowance for doubtful accounts		205		221
	Receivables, net	$	6,321	$	6,376
	In addition to the amounts in the table above, noncurrent receivables of $569 million and $488 million as of December 31, 2014 and 2013, respectively, are included in other noncurrent assets, net that primarily relate to the licensing of our television and film productions to third parties.
	Cash Payments for Interest and Income Taxes
	Year ended December 31 (in millions)		2014		2013		2012
	Interest	$	2,389	$	2,355	$	2,314
	Income taxes	$	3,668	$	3,946	$	2,841
	Noncash Investing and Financing Activities
	During 2014:
	• we acquired $797 million of property and equipment and intangible assets that were accrued but unpaid
	• we recorded a liability of $572 million for a quarterly cash dividend of $0.225 per common share paid in January 2015
	• we used $3.2 billion of equity securities to settle a portion of our obligations under prepaid forward sale agreements
	During 2013:
	• we acquired GE’s 49% common equity interest in NBCUniversal Holdings that we did not already own for total consideration of $16.7 billion, which included noncash consideration of $6 billion that was comprised of $4 billion aggregate principal amount of senior notes issued by NBCUniversal Enterprise, $1.25 billion of borrowings under NBCUniversal Enterprise’s credit facility and $725 million aggregate liquidation preference of NBCUniversal Enterprise Series A cumulative preferred stock (see Note 5 for additional information on the NBCUniversal redemption transaction)
	• we acquired $872 million of property and equipment and intangible assets that were accrued but unpaid
	• we recorded a liability of $509 million for a quarterly cash dividend of $0.195 per common share paid in January 2014
	• we used $1.4 billion of equity securities to settle a portion of our obligations under prepaid forward sale agreements
	• we closed a transaction with Liberty Media that included, among other things, the delivery of Liberty Media shares owned by us in exchange for Liberty Media’s interests in one of NBCUniversal’s contractual obligations (see Note 7 for additional information)
	During 2012:
	• we acquired $757 million of property and equipment and intangible assets that were accrued but unpaid
	• we recorded a liability of $430 million for a quarterly cash dividend of $0.1625 per common share paid in January 2013
	• NBCUniversal entered into a capital lease transaction that resulted in an increase in property and equipment and debt of $85 million
NBCUniversal Media, LLC [Member]
Supplemental Financial Information	Note 15: Supplemental Financial Information
	Receivables
	December 31 (in millions)		2014		2013
	Receivables, gross	$	5,258	$	5,348
	Less: Allowance for returns and customer incentives		356		372
	Less: Allowance for doubtful accounts		60		65
	Receivables, net	$	4,842	$	4,911
	In addition to the amounts in the table above, noncurrent receivables of $569 million and $488 million as of December 31, 2014 and 2013, respectively, are included in other noncurrent assets, net that primarily relate to the licensing of our television and film productions to third parties.
	Accumulated Other Comprehensive Income (Loss)
	December 31 (in millions)		2014		2013
	Deferred gains (losses) on cash flow hedges		$	20	$	-5
	Unrecognized gains (losses) on employee benefit obligations			-61		45
	Cumulative translation adjustments			-118		-56
	Accumulated other comprehensive income (loss)		$	-159	$	-16
	Cash Payments for Interest and Income Taxes
	Year ended December 31 (in millions)	2014		2013			2012
	Interest	$	485	$	462	$	461
	Income taxes	$	174	$	205	$	169
	Noncash Investing and Financing Activities
	During 2014:
	we acquired $148 million of property and equipment and intangible assets that were accrued but unpaid
	During 2013:
	we acquired $306 million of property and equipment and intangible assets that were accrued but unpaid
	During 2012:
	we entered into a capital lease transaction that resulted in an increase in property and equipment and debt of $85 million

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies	Note 17: Commitments and Contingencies
	Commitments
	NBCUniversal enters into long-term commitments with third parties in the ordinary course of its business, including commitments to acquire film and television programming, creative talent and employment agreements, and various other television-related commitments. Many of NBCUniversal’s employees, including writers, directors, actors, technical and production personnel, and others, as well as some of its on-air and creative talent, are covered by collective bargaining agreements or works councils. As of December 31, 2014, the total number of NBCUniversal full-time, part-time and hourly employees on its payroll covered by collective bargaining agreements was 7,400 full-time equivalent employees. Of this total, approximately 30% of these full-time equivalent employees were covered by collective bargaining agreements that have expired or are scheduled to expire during 2015.
	We, through Comcast-Spectacor, have employment agreements with both players and coaches of the Philadelphia Flyers. Certain of these employment agreements, which provide for payments that are guaranteed regardless of employee injury or termination, are covered by disability insurance if certain conditions are met.
	The table below summarizes our minimum annual programming and talent commitments and our minimum annual rental commitments for office space, equipment and transponder service agreements under operating leases. Programming and talent commitments include acquired film and television programming, including U.S. television rights to the Olympic Games through 2032, Sunday Night Football on NBC through the 2022-23 season, and other programming commitments, as well as various contracts with creative talent and employment agreements.
	As of December 31, 2014 (in millions)		Programming and Talent Commitments		Operating Leases
	2015	$	4,915	$	399
	2016	$	4,657	$	359
	2017	$	3,177	$	299
	2018	$	3,999	$	253
	2019	$	2,793	$	197
	Thereafter	$	26,130	$	754
	The table below presents our rent expense charged to operations.
	Year ended December 31 (in millions)		2014		2013		2012
	Rent expense	$	580	$	616	$	688
	Contingencies
	Antitrust Cases
	We are defendants in two purported class actions originally filed in December 2003 in the United States District Courts for the District of Massachusetts and the Eastern District of Pennsylvania. The potential class in the Massachusetts case, which has been transferred to the Eastern District of Pennsylvania, is our customer base in the “Boston Cluster” area, and the potential class in the Pennsylvania case is our customer base in the “Philadelphia and Chicago Clusters,” as those terms are defined in the complaints. In each case, the plaintiffs allege that certain customer exchange transactions with other cable providers resulted in unlawful horizontal market restraints in those areas and seek damages under antitrust statutes, including treble damages.
	Classes of Chicago Cluster and Philadelphia Cluster customers were certified in October 2007 and January 2010, respectively. We appealed the class certification in the Philadelphia Cluster case to the Third Circuit Court of Appeals, which affirmed the class certification in August 2011. In June 2012, the U.S. Supreme Court granted our petition to review the Third Circuit Court of Appeals’ ruling and in March 2013, the Supreme Court ruled that the class had been improperly certified and reversed the judgment of the Third Circuit. In August 2013, the plaintiffs in the Philadelphia Cluster case moved to certify a new, smaller class, which we opposed in January 2014. The parties have been discussing possible resolution of the Philadelphia Cluster case. Accordingly, in February 2014, the plaintiff filed an unopposed motion to stay the case, which the District Court granted. In April 2014, the District Court granted our unopposed motion to de-certify the Chicago Cluster class and the plaintiffs’ unopposed motion to amend the Pennsylvania case so as to dismiss claims relating to the Chicago Cluster. In April 2014, lead counsel for the Boston Cluster cases withdrew, and in June 2014, new counsel requested the Boston Cluster cases be transferred to the federal court in Boston, which we have opposed. The District Court denied the request and dismissed the case, though the Boston plaintiffs have appealed both rulings. In December 2014, the District Court granted preliminary approval to a settlement of the Philadelphia Cluster case, which contains no admission or finding of liability. We do not expect the settlement of the Philadelphia Cluster case to have a material effect on our results of operations, cash flows or financial position.
	In addition, we are the defendant in 23 putative class actions filed in federal district courts throughout the country. All of these actions have been consolidated by the Judicial Panel on Multidistrict Litigation in the United States District Court for the Eastern District of Pennsylvania for pre-trial proceedings. In a consolidated complaint filed in November 2009 on behalf of all plaintiffs in the multidistrict litigation, the plaintiffs allege that we improperly “tie” the rental of set-top boxes to the provision of premium cable services in violation of Section 1 of the Sherman Antitrust Act, various state antitrust laws and unfair/deceptive trade practices acts in California, Illinois and Alabama. The plaintiffs also allege a claim for unjust enrichment and seek relief on behalf of a nationwide class of our premium cable customers and on behalf of subclasses consisting of premium cable customers from California, Alabama, Illinois, Pennsylvania and Washington. In January 2010, we moved to compel arbitration of the plaintiffs’ claims for unjust enrichment and violations of the unfair/deceptive trade practices acts of Illinois and Alabama. In September 2010, the plaintiffs filed an amended complaint alleging violations of additional state antitrust laws and unfair/deceptive trade practices acts on behalf of new subclasses in Connecticut, Florida, Minnesota, Missouri, New Jersey, New Mexico and West Virginia. In the amended complaint, plaintiffs omitted their unjust enrichment claim, as well as their state law claims on behalf of the Alabama, Illinois and Pennsylvania subclasses. In June 2011, the plaintiffs filed another amended complaint alleging only violations of Section 1 of the Sherman Antitrust Act, antitrust law in Washington and unfair/deceptive trade practices acts in California and Washington. The plaintiffs seek relief on behalf of a nationwide class of our premium cable customers and on behalf of subclasses consisting of premium cable customers from California and Washington. In July 2011, we moved to compel arbitration of most of the plaintiffs’ claims and to stay the remaining claims pending arbitration. The West Virginia Attorney General also filed a complaint in West Virginia state court in July 2009 alleging that we improperly “tie” the rental of set-top boxes to the provision of digital cable services in violation of the West Virginia Antitrust Act and the West Virginia Consumer Credit and Protection Act. The Attorney General also alleges a claim for unjust enrichment/restitution. We removed the case to the United States District Court for West Virginia, and it was subsequently transferred to the United States District Court for the Eastern District of Pennsylvania and consolidated with the multidistrict litigation described above. A comprehensive settlement agreement for all 23 cases that had been submitted to the District Court for preliminary approval in June 2013 was withdrawn in October 2014, and we refiled our motion to compel arbitration. We do not expect these cases to have a material effect on our results of operations, cash flows or financial position.
	Other
	We are a defendant in several unrelated lawsuits claiming infringement of various patents relating to various aspects of our businesses. In certain of these cases other industry participants are also defendants, and also in certain of these cases we expect that any potential liability would be in part or in whole the responsibility of our equipment and technology vendors under applicable contractual indemnification provisions. We are also subject to other legal proceedings and claims that arise in the ordinary course of our business. While the amount of ultimate liability with respect to such actions is not expected to materially affect our results of operations, cash flows or financial position, any litigation resulting from any such legal proceedings or claims could be time-consuming and injure our reputation.
NBCUniversal Media, LLC [Member]
Commitments and Contingencies	Note 16: Commitments and Contingencies
	Commitments
	We enter into long-term commitments with third parties in the ordinary course of our business, including commitments to acquire film and television programming, creative talent and employment agreements, and various other television-related commitments. Many of our employees, including writers, directors, actors, technical and production personnel, and others, as well as some of our on-air and creative talent, are covered by collective bargaining agreements or works councils. As of December 31, 2014, the total number of full-time, part-time and hourly employees on our payroll covered by collective bargaining agreements was 7,400 full-time equivalent employees. Of this total, approximately 30% of these full-time equivalent employees were covered by collective bargaining agreements that have expired or are scheduled to expire during 2015.
	The table below summarizes our minimum annual programming and talent commitments and our minimum annual rental commitments for office space and equipment under operating leases. Programming and talent commitments include acquired film and television programming, including U.S. television rights to the Olympic Games through 2032, Sunday Night Football on NBC through the 2022-23 season, and other programming commitments, as well as various contracts with creative talent and employment agreements.
	As of December 31, 2014 (in millions)		Programming and Talent Commitments		Operating Leases
	2015	$	4,898	$	150
	2016	$	4,648	$	135
	2017	$	3,173	$	107
	2018	$	3,998	$	89
	2019	$	2,793	$	73
	Thereafter	$	26,130	$	402
	The table below presents our rent expense charged to operations.
	Year ended December 31 (in millions)	2014		2013		2012
	Rent expense	$	222	$	250	$	317

Financial_Data_by_Business_Seg

Financial Data by Business Segment	12 Months Ended
	Dec. 31, 2014
Financial Data by Business Segment	Note 18: Financial Data by Business Segment
	We present our operations in one reportable business segment for Cable Communications and four reportable business segments for NBCUniversal. The Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks segments comprise the NBCUniversal businesses and are collectively referred to as the NBCUniversal segments. Our financial data by reportable business segment is presented in the tables below.
	(in millions)			Revenue(f)		Operating Income (Loss) Before Depreciation and Amortization(g)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2014
	Cable Communications(a)		$	44,140	$	18,112	$	6,422	$	11,690	$	6,154	$	140,616
	NBCUniversal
		Cable Networks(b)(c)		9,563		3,589		748		2,841		49		28,582
		Broadcast Television(c)		8,542		734		127		607		76		6,806
		Filmed Entertainment(b)		5,008		711		21		690		11		4,185
		Theme Parks		2,623		1,168		273		895		671		7,017
		Headquarters and Other(d)		13		-613		326		-939		414		6,479
		Eliminations(e)		-321		-1		-		-1		-		-452
	NBCUniversal			25,428		5,588		1,495		4,093		1,221		52,617
	Corporate and Other			709		-778		102		-880		45		5,338
	Eliminations(e)			-1,502		1		-		1		-		-39,232
	Comcast Consolidated		$	68,775	$	22,923	$	8,019	$	14,904	$	7,420	$	159,339
	(in millions)			Revenue(f)		Operating Income (Loss) Before Depreciation and Amortization(g)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2013
	Cable Communications(a)		$	41,836	$	17,205	$	6,394	$	10,811	$	5,403	$	132,082
	NBCUniversal
		Cable Networks(b)		9,201		3,501		734		2,767		67		29,413
		Broadcast Television		7,120		345		98		247		65		6,723
		Filmed Entertainment(b)		5,452		483		15		468		9		3,549
		Theme Parks		2,235		1,004		300		704		580		6,608
		Headquarters and Other(d)		31		-588		264		-852		439		6,002
		Eliminations(e)		-389		-13		-		-13		-		-556
	NBCUniversal			23,650		4,732		1,411		3,321		1,160		51,739
	Corporate and Other			600		-489		66		-555		33		8,152
	Eliminations(e)			-1,429		-14		-		-14		-		-33,160
	Comcast Consolidated		$	64,657	$	21,434	$	7,871	$	13,563	$	6,596	$	158,813
	(in millions)			Revenue(f)		Operating Income (Loss) Before Depreciation and Amortization(g)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures
	2012
	Cable Communications(a)		$	39,604	$	16,255	$	6,405	$	9,850	$	4,921
	NBCUniversal
		Cable Networks(b)		8,727		3,303		735		2,568		150
		Broadcast Television(c)		8,200		358		97		261		65
		Filmed Entertainment(b)		5,159		79		16		63		7
		Theme Parks		2,085		953		268		685		272
		Headquarters and Other(d)		43		-603		210		-813		269
		Eliminations(e)		-402		17		-		17		-
	NBCUniversal			23,812		4,107		1,326		2,781		763
	Corporate and Other			498		-376		67		-443		30
	Eliminations(e)			-1,344		-9		-		-9		-
	Comcast Consolidated		$	62,570	$	19,977	$	7,798	$	12,179	$	5,714
	(a) For the years ended December 31, 2014, 2013 and 2012, Cable Communications segment revenue was derived from the following sources:
			2014		2013		2012
	Residential:
		Video	47.1	%	49.1	%	50.4	%
		High-speed Internet	25.6	%	24.7	%	24.1	%
		Voice	8.3	%	8.7	%	9	%
	Business services		9	%	7.7	%	6.5	%
	Advertising		5.5	%	5.2	%	5.8	%
	Other		4.5	%	4.6	%	4.2	%
	Total		100	%	100	%	100	%
	Subscription revenue received from customers who purchase bundled services at a discounted rate is allocated proportionally to each service based on the individual service’s price on a stand-alone basis.
	For each of 2014, 2013 and 2012, 2.8% of Cable Communications revenue was derived from franchise and other regulatory fees.
	(b) Beginning in 2014, Fandango, our movie ticketing and entertainment business that was previously presented in our Cable Networks segment, is now presented in the Filmed Entertainment segment to reflect the change in our management reporting presentation. Due to immateriality, prior period amounts have not been adjusted.
	(c) The revenue and operating costs and expenses associated with our broadcast of the 2014 Sochi Olympics were reported in our Cable Networks and Broadcast Television segments. The revenue and operating costs and expenses associated with our broadcasts of the 2012 London Olympics and the 2012 Super Bowl were reported in our Broadcast Television segment.
	(d) NBCUniversal Headquarters and Other activities include costs associated with overhead, allocations, personnel costs and headquarter initiatives.
	(e) Included in Eliminations are transactions that our segments enter into with one another. The most common types of transactions are the following:
	• our Cable Networks and Broadcast Television segments generate revenue by selling programming to our Cable Communications segment, which represents a substantial majority of the revenue elimination amount
	• our Cable Communications segment generates revenue by selling advertising and by selling the use of satellite feeds to our Cable Networks segment
	• our Filmed Entertainment and Broadcast Television segments generate revenue by licensing content to our Cable Networks segment
	• our Cable Communications segment receives incentives offered by our Cable Networks segment in connection with its distribution of the Cable Networks’ content that are recorded as a reduction to programming expenses
(f) Revenue from customers located outside of the United States, primarily in Europe and Asia, for the years ended December 31, 2014, 2013 and 2012 was $4.4 billion, $4.8 billion and $4.5 billion, respectively. No single customer accounted for a significant amount of revenue in any period.
(g) We use operating income (loss) before depreciation and amortization, excluding impairment charges related to fixed and intangible assets and gains or losses from the sale of assets, if any, as the measure of profit or loss for our operating segments. This measure eliminates the significant level of noncash depreciation and amortization expense that results from the capital-intensive nature of certain of our businesses and from intangible assets recognized in business combinations. Additionally, it is unaffected by our capital structure or investment activities. We use this measure to evaluate our consolidated operating performance and the operating performance of our operating segments and to allocate resources and capital to our operating segments. It is also a significant performance measure in our annual incentive compensation programs. We believe that this measure is useful to investors because it is one of the bases for comparing our operating performance with that of other companies in our industries, although our measure may not be directly comparable to similar measures used by other companies. This measure should not be considered a substitute for operating income (loss), net income (loss) attributable to Comcast Corporation, net cash provided by operating activities, or other measures of performance or liquidity we have reported in accordance with GAAP.
NBCUniversal Media, LLC [Member]
Financial Data by Business Segment	Note 17: Financial Data by Business Segment
	We present our operations in four reportable business segments: Cable Networks, Broadcast Television, Filmed Entertainment and Theme Parks. Our financial data by reportable business segment is presented in the tables below.
	(in millions)			Revenue(e)(g)		Operating Income (Loss) Before Depreciation and Amortization(f)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2014
		Cable Networks(a)(b)	$	9,563	$	3,589	$	748	$	2,841	$	49	$	28,582
		Broadcast Television(b)		8,542		734		127		607		76		6,806
		Filmed Entertainment(a)		5,008		711		21		690		11		4,185
		Theme Parks		2,623		1,168		273		895		671		7,017
		Headquarters and Other(c)		13		-613		326		-939		414		6,479
		Eliminations(d)		-321		-1		-		-1		-		-452
	Total		$	25,428	$	5,588	$	1,495	$	4,093	$	1,221	$	52,617
	(in millions)			Revenue(e)(g)		Operating Income (Loss) Before Depreciation and Amortization(f)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2013
		Cable Networks(a)	$	9,201	$	3,501	$	734	$	2,767	$	67	$	29,413
		Broadcast Television		7,120		345		98		247		65		6,723
		Filmed Entertainment(a)		5,452		483		15		468		9		3,549
		Theme Parks		2,235		1,004		300		704		580		6,608
		Headquarters and Other(c)		31		-588		264		-852		439		6,002
		Eliminations(d)		-389		-13		-		-13		-		-556
	Total		$	23,650	$	4,732	$	1,411	$	3,321	$	1,160	$	51,739
	(in millions)			Revenue(e)(g)		Operating Income (Loss) Before Depreciation and Amortization(f)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures
	2012
		Cable Networks(a)	$	8,727	$	3,303	$	735	$	2,568	$	150
		Broadcast Television(b)		8,200		358		97		261		65
		Filmed Entertainment(a)		5,159		79		16		63		7
		Theme Parks		2,085		953		268		685		272
		Headquarters and Other(c)		43		-603		210		-813		269
		Eliminations(d)		-402		17		-		17		-
	Total		$	23,812	$	4,107	$	1,326	$	2,781	$	763
	Beginning in 2014, Fandango, our movie ticketing and entertainment business that was previously presented in our Cable Networks segment, is now presented in the Filmed Entertainment segment to reflect the change in our management reporting presentation. Due to immateriality, prior period amounts have not been adjusted.
	The revenue and operating costs and expenses associated with our broadcast of the 2014 Sochi Olympics were reported in our Cable Networks and Broadcast Television segments. The revenue and operating costs and expenses associated with our broadcasts of the 2012 London Olympics and the 2012 Super Bowl were reported in our Broadcast Television segment.
	Headquarters and Other activities include costs associated with overhead, allocations, personnel costs and corporate initiatives.
	Eliminations are transactions that our segments enter into with one another, which consisted primarily of the licensing of film and television content from our Filmed Entertainment and Broadcast Television segments to our Cable Networks segment.
	No single customer accounted for a significant amount of revenue in any period.
	We use operating income (loss) before depreciation and amortization, excluding impairment charges related to fixed and intangible assets and gains or losses from the sale of assets, if any, as the measure of profit or loss for our operating segments. This measure eliminates the significant level of noncash amortization expense that results from intangible assets recognized in connection with the joint venture transaction and other business combinations. Additionally, it is unaffected by our capital structure or investment activities. We use this measure to evaluate our consolidated operating performance and the operating performance of our operating segments and to allocate resources and capital to our operating segments. It is also a significant performance measure in our annual incentive compensation programs. We believe that this measure is useful to investors because it is one of the bases for comparing our operating performance with that of other companies in our industries, although our measure may not be directly comparable to similar measures used by other companies. This measure should not be considered a substitute for operating income (loss), net income (loss) attributable to NBCUniversal, net cash provided by operating activities, or other measures of performance or liquidity we have reported in accordance with GAAP.
	We operate primarily in the United States, but also in select international markets primarily in Europe and Asia. The table below summarizes revenue by geographic location.
		Year ended December 31 (in millions)		2014		2013		2012
		Revenue:
		United States	$	20,995	$	18,887	$	19,348
		Foreign	$	4,433	$	4,763	$	4,464

Quarterly_Financial_Informatio

Quarterly Financial Information	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information	Note 19: Quarterly Financial Information (Unaudited)
	(in millions, except per share data)		First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
	2014
	Revenue	$	17,408	$	16,844	$	16,791	$	17,732	$	68,775
	Operating income	$	3,568	$	3,804	$	3,745	$	3,787	$	14,904
	Net income attributable to Comcast Corporation(a)	$	1,871	$	1,992	$	2,592	$	1,925	$	8,380
	Basic earnings per common share attributable to Comcast Corporation shareholders	$	0.72	$	0.77	$	1	$	0.75	$	3.24
	Diluted earnings per common share attributable to Comcast Corporation shareholders	$	0.71	$	0.76	$	0.99	$	0.74	$	3.2
	Dividends declared per common share	$	0.225	$	0.225	$	0.225	$	0.225	$	0.9
	2013
	Revenue	$	15,310	$	16,270	$	16,151	$	16,926	$	64,657
	Operating income	$	3,067	$	3,435	$	3,414	$	3,647	$	13,563
	Net income attributable to Comcast Corporation	$	1,437	$	1,734	$	1,732	$	1,913	$	6,816
	Basic earnings per common share attributable to Comcast Corporation shareholders	$	0.55	$	0.66	$	0.66	$	0.73	$	2.6
	Diluted earnings per common share attributable to Comcast Corporation shareholders	$	0.54	$	0.65	$	0.65	$	0.72	$	2.56
	Dividends declared per common share	$	0.195	$	0.195	$	0.195	$	0.195	$	0.78
	(a) In the third quarter of 2014, net income attributable to Comcast Corporation included $724 million of favorable income tax adjustments resulting from a reduction in our accruals for uncertain tax positions and the related accrued interest on these tax positions. See Note 15 for additional information.

Condensed_Consolidating_Financ

Condensed Consolidating Financial Information	12 Months Ended
	Dec. 31, 2014
Condensed Consolidating Financial Information [Abstract]
Condensed Consolidating Financial Information	Note 20: Condensed Consolidating Financial Information
	Comcast (“Comcast Parent”), Comcast Cable Communications, LLC (“CCCL Parent”), Comcast MO Group, Inc. (“Comcast MO Group”), Comcast Cable Holdings, LLC (“CCH”) and Comcast MO of Delaware, LLC (“Comcast MO of Delaware”) (collectively, the “cable guarantors”) and NBCUniversal (“NBCUniversal Media Parent”) have fully and unconditionally guaranteed each other’s debt securities. In addition, the Comcast and Comcast Cable Communications, LLC $6.25 billion revolving credit facility due June 2017 and the Comcast commercial paper program are also fully and unconditionally guaranteed by NBCUniversal. The Comcast commercial paper program is supported by the Comcast and Comcast Cable Communications, LLC revolving credit facility. Comcast MO Group, CCH and Comcast MO of Delaware are collectively referred to as the “Combined CCHMO Parents.” The debt securities within the guarantee structure total $32.6 billion, of which $9.3 billion will mature within the next five years.
	Comcast Parent and the cable guarantors also fully and unconditionally guarantee NBCUniversal Enterprise’s $4 billion of senior notes, as well as its $1.35 billion credit facility due March 2018 and the associated commercial paper program. NBCUniversal Media Parent does not guarantee the NBCUniversal Enterprise senior notes, credit facility or commercial paper program.
	Comcast Parent provides an unconditional subordinated guarantee of the $185 million principal amount currently outstanding of Comcast Holdings’ ZONES due October 2029. Neither the cable guarantors nor NBCUniversal Media Parent guarantee the Comcast Holdings’ ZONES due October 2029. None of Comcast Parent, the cable guarantors nor NBCUniversal Media Parent guarantee the $62 million principal amount currently outstanding of Comcast Holdings’ ZONES due November 2029.
	Condensed Consolidating Balance Sheet
	December 31, 2014 (in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Assets
		Cash and cash equivalents	$	-	$	-	$	-	$	-	$	385	$	3,525	$	-	$	3,910
		Investments		-		-		-		-		-		602		-		602
		Receivables, net		-		-		-		-		-		6,321		-		6,321
		Programming rights		-		-		-		-		-		839		-		839
		Other current assets		267		-		-		-		41		1,551		-		1,859
	Total current assets			267		-		-		-		426		12,838		-		13,531
	Film and television costs			-		-		-		-		-		5,727		-		5,727
	Investments			36		-		-		-		378		2,721		-		3,135
	Investments in and amounts due from subsidiaries eliminated upon consolidation			84,142		103,420		110,323		58,677		41,239		98,152		-495,953		-
	Property and equipment, net			199		-		-		-		-		30,754		-		30,953
	Franchise rights			-		-		-		-		-		59,364		-		59,364
	Goodwill			-		-		-		-		-		27,316		-		27,316
	Other intangible assets, net			11		-		-		-		-		16,969		-		16,980
	Other noncurrent assets, net			1,224		148		-		-		92		1,949		-1,080		2,333
	Total assets		$	85,879	$	103,568	$	110,323	$	58,677	$	42,135	$	255,790	$	-497,033	$	159,339
	Liabilities and Equity
		Accounts payable and accrued expenses related to trade creditors	$	19	$	-	$	-	$	1	$	-	$	5,618	$	-	$	5,638
		Accrued participations and residuals		-		-		-		-		-		1,347		-		1,347
		Accrued expenses and other current liabilities		1,547		283		233		47		331		3,767		-		6,208
		Current portion of long-term debt		1,650		-		-		677		1,006		884		-		4,217
	Total current liabilities			3,216		283		233		725		1,337		11,616		-		17,410
	Long-term debt, less current portion			27,616		126		1,827		822		9,218		4,408		-		44,017
	Deferred income taxes			-		701		-		-		67		33,127		-936		32,959
	Other noncurrent liabilities			2,336		-		-		-		1,143		7,484		-144		10,819
	Redeemable noncontrolling interests
		and redeemable subsidiary preferred stock		-		-		-		-		-		1,066		-		1,066
	Equity:
		Common stock		30		-		-		-		-		-		-		30
		Other shareholders’ equity		52,681		102,458		108,263		57,130		30,370		197,732		-495,953		52,681
	Total Comcast Corporation shareholders’ equity			52,711		102,458		108,263		57,130		30,370		197,732		-495,953		52,711
	Noncontrolling interests			-		-		-		-		-		357		-		357
	Total equity			52,711		102,458		108,263		57,130		30,370		198,089		-495,953		53,068
	Total liabilities and equity		$	85,879	$	103,568	$	110,323	$	58,677	$	42,135	$	255,790	$	-497,033	$	159,339
	Condensed Consolidating Balance Sheet
	December 31, 2013(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Assets
		Cash and cash equivalents	$	-	$	-	$	-	$	-	$	336	$	1,382	$	-	$	1,718
		Investments		-		-		-		-		-		3,573		-		3,573
		Receivables, net		-		-		-		-		-		6,376		-		6,376
		Programming rights		-		-		-		-		-		928		-		928
		Other current assets		237		-		-		-		35		1,208		-		1,480
	Total current assets			237		-		-		-		371		13,467		-		14,075
	Film and television costs			-		-		-		-		-		4,994		-		4,994
	Investments			11		-		-		-		374		3,385		-		3,770
	Investments in and amounts due from subsidiaries eliminated upon consolidation			79,956		97,429		102,673		54,724		40,644		85,164		-460,590		-
	Property and equipment, net			220		-		-		-		-		29,620		-		29,840
	Franchise rights			-		-		-		-		-		59,364		-		59,364
	Goodwill			-		-		-		-		-		27,098		-		27,098
	Other intangible assets, net			11		-		-		-		-		17,318		-		17,329
	Other noncurrent assets, net			1,078		145		-		-		103		1,899		-882		2,343
	Total assets		$	81,513	$	97,574	$	102,673	$	54,724	$	41,492	$	242,309	$	-461,472	$	158,813
	Liabilities and Equity
		Accounts payable and accrued expenses related to trade creditors	$	8	$	-	$	-	$	-	$	-	$	5,520	$	-	$	5,528
		Accrued participations and residuals		-		-		-		-		-		1,239		-		1,239
		Accrued expenses and other current liabilities		1,371		266		180		47		323		6,678		-		8,865
		Current portion of long-term debt		2,351		-		-		-		903		26		-		3,280
	Total current liabilities			3,730		266		180		47		1,226		13,463		-		18,912
Long-term debt, less current portion			25,170		132		1,827		1,505		10,236		5,697		-		44,567
Deferred income taxes			-		777		-		-		59		31,840		-741		31,935
Other noncurrent liabilities			1,919		-		-		-		931		8,675		-141		11,384
Redeemable noncontrolling interests
	and redeemable subsidiary preferred stock		-		-		-		-		-		957		-		957
Equity:
	Common stock		30		-		-		-		-		-		-		30
	Other shareholders’ equity		50,664		96,399		100,666		53,172		29,040		181,313		-460,590		50,664
Total Comcast Corporation shareholders’ equity			50,694		96,399		100,666		53,172		29,040		181,313		-460,590		50,694
Noncontrolling interests			-		-		-		-		-		364		-		364
Total equity			50,694		96,399		100,666		53,172		29,040		181,677		-460,590		51,058
Total liabilities and equity		$	81,513	$	97,574	$	102,673	$	54,724	$	41,492	$	242,309	$	-461,472	$	158,813
Condensed Consolidating Statement of Income
For the Year Ended December 31, 2014(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
Revenue:
	Service revenue	$	-	$	-	$	-	$	-	$	-	$	68,775	$	-	$	68,775
	Management fee revenue		947		-		921		582		-		-		-2,450		-
			947		-		921		582		-		68,775		-2,450		68,775
Costs and Expenses:
	Programming and production		-		-		-		-		-		20,912		-		20,912
	Other operating and administrative		751		-		921		582		908		19,150		-2,450		19,862
	Advertising, marketing and promotion		-		-		-		-		-		5,078		-		5,078
	Depreciation		34		-		-		-		-		6,303		-		6,337
	Amortization		6		-		-		-		-		1,676		-		1,682
			791		-		921		582		908		53,119		-2,450		53,871
Operating income (loss)			156		-		-		-		-908		15,656		-		14,904
Other Income (Expense):
	Interest expense		-1,621		-11		-176		-118		-479		-212		-		-2,617
	Investment income (loss), net		3		12		-		-		-7		288		-		296
	Equity in net income (losses) of
	investees, net		9,330		8,843		8,273		6,333		4,523		3,212		-40,417		97
	Other income (expense), net		-		-		-		-		-4		-211		-		-215
			7,712		8,844		8,097		6,215		4,033		3,077		-40,417		-2,439
Income (loss) before income taxes			7,868		8,844		8,097		6,215		3,125		18,733		-40,417		12,465
Income tax (expense) benefit			512		-		62		41		-10		-4,478		-		-3,873
Net income (loss)			8,380		8,844		8,159		6,256		3,115		14,255		-40,417		8,592
Net (income) loss attributable to
	noncontrolling interests and redeemable subsidiary preferred stock		-		-		-		-		-		-212		-		-212
Net income (loss) attributable to
	Comcast Corporation	$	8,380	$	8,844	$	8,159	$	6,256	$	3,115	$	14,043	$	-40,417	$	8,380
Comprehensive income (loss)
	attributable to Comcast Corporation	$	8,178	$	8,807	$	8,162	$	6,257	$	2,972	$	13,980	$	-40,178	$	8,178
Condensed Consolidating Statement of Income
For the Year Ended December 31, 2013(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
Revenue:
	Service revenue	$	-	$	-	$	-	$	-	$	-	$	64,657	$	-	$	64,657
	Management fee revenue		897		-		874		548		-		-		-2,319		-
			897		-		874		548		-		64,657		-2,319		64,657
Costs and Expenses:
	Programming and production		-		-		-		-		-		19,670		-		19,670
	Other operating and administrative		403		-		874		548		855		18,223		-2,319		18,584
	Advertising, marketing and promotion		-		-		-		-		-		4,969		-		4,969
	Depreciation		30		-		-		-		-		6,224		-		6,254
	Amortization		5		-		-		-		-		1,612		-		1,617
			438		-		874		548		855		50,698		-2,319		51,094
Operating income (loss)			459		-		-		-		-855		13,959		-		13,563
Other Income (Expense):
	Interest expense		-1,523		-11		-212		-126		-488		-214		-		-2,574
	Investment income (loss), net		-		-13		-		-		3		586		-		576
	Equity in net income (losses) of
	investees, net		7,509		7,540		7,430		5,473		3,331		1,882		-33,251		-86
	Other income (expense), net		-2		-		2		-		-1		-363		-		-364
			5,984		7,516		7,220		5,347		2,845		1,891		-33,251		-2,448
Income (loss) before income taxes			6,443		7,516		7,220		5,347		1,990		15,850		-33,251		11,115
Income tax (expense) benefit			373		9		73		44		-22		-4,457		-		-3,980
Net income (loss)			6,816		7,525		7,293		5,391		1,968		11,393		-33,251		7,135
Net (income) loss attributable to
	noncontrolling interests and redeemable subsidiary preferred stock		-		-		-		-		-		-319		-		-319
Net income (loss) attributable
	to Comcast Corporation	$	6,816	$	7,525	$	7,293	$	5,391	$	1,968	$	11,074	$	-33,251	$	6,816
Comprehensive income (loss)
	attributable to Comcast Corporation	$	6,883	$	7,521	$	7,276	$	5,392	$	2,017	$	10,969	$	-33,175	$	6,883
Condensed Consolidating Statement of Income
For the Year Ended December 31, 2012(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
Revenue:
	Service revenue	$	-	$	-	$	-	$	-	$	-	$	62,570	$	-	$	62,570
	Management fee revenue		848		-		827		516		-		-		-2,191		-
			848		-		827		516		-		62,570		-2,191		62,570
Costs and Expenses:
	Programming and production		-		-		-		-		-		19,929		-		19,929
	Other operating and administrative		401		-		827		516		899		17,381		-2,191		17,833
	Advertising, marketing and promotion		-		-		-		-		-		4,831		-		4,831
	Depreciation		30		-		-		-		-		6,120		-		6,150
	Amortization		4		-		-		-		-		1,644		-		1,648
			435		-		827		516		899		49,905		-2,191		50,391
Operating income (loss)			413		-		-		-		-899		12,665		-		12,179
Other Income (Expense):
	Interest expense		-1,430		-23		-329		-135		-430		-174		-		-2,521
	Investment income (loss), net		8		3		-		-		5		203		-		219
	Equity in net income (losses) of
	investees, net		6,858		6,536		6,665		4,909		4,402		4,014		-32,425		959
	Other income (expense), net		2		-		-		-		-14		785		-		773
			5,438		6,516		6,336		4,774		3,963		4,828		-32,425		-570
Income (loss) before income taxes			5,851		6,516		6,336		4,774		3,064		17,493		-32,425		11,609
Income tax (expense) benefit			352		7		115		47		-9		-4,256		-		-3,744
Net income (loss)			6,203		6,523		6,451		4,821		3,055		13,237		-32,425		7,865
Net (income) loss attributable to
	noncontrolling interests and redeemable subsidiary preferred stock		-		-		-		-		-		-1,662		-		-1,662
Net income (loss) attributable to
	Comcast Corporation	$	6,203	$	6,523	$	6,451	$	4,821	$	3,055	$	11,575	$	-32,425	$	6,203
Comprehensive income (loss)
	attributable to Comcast Corporation	$	6,370	$	6,523	$	6,460	$	4,821	$	3,068	$	11,703	$	-32,575	$	6,370
Condensed Consolidating Statement of Cash Flows
For the Year Ended December 31, 2014(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Net cash provided by (used in) operating activities	$	-354	$	9	$	-57	$	-82	$	-1,299	$	18,728	$	-	$	16,945
Investing Activities:
	Net transactions with affiliates		4,784		-9		57		82		2,247		-7,161		-		-
	Capital expenditures		-3		-		-		-		-		-7,417		-		-7,420
	Cash paid for intangible assets		-6		-		-		-		-		-1,116		-		-1,122
	Acquisitions and construction of real estate properties		-		-		-		-		-		-43		-		-43
	Acquisitions, net of cash acquired		-		-		-		-		-		-477		-		-477
	Proceeds from sales of businesses and investments		-		-		-		-		8		658		-		666
	Return of capital from investees		-		-		-		-		1		24		-		25
	Purchases of investments		-19		-		-		-		-10		-162		-		-191
	Other		-		-		-		-		4		-175		-		-171
	Net cash provided by (used in) investing activities		4,756		-9		57		82		2,250		-15,869		-		-8,733
Financing Activities:
	Proceeds from (repayments of) short-term borrowings, net		-1,350		-		-		-		-		846		-		-504
	Proceeds from borrowings		4,180		-		-		-		-		2		-		4,182
	Repurchases and repayments of debt		-1,000		-		-		-		-902		-1,273		-		-3,175
	Repurchases and retirements of common stock		-4,251		-		-		-		-		-		-		-4,251
	Dividends paid		-2,254		-		-		-		-		-		-		-2,254
	Issuances of common stock		35		-		-		-		-		-		-		35
	Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock		-		-		-		-		-		-220		-		-220
	Other		238		-		-		-		-		-71		-		167
	Net cash provided by (used in) financing activities		-4,402		-		-		-		-902		-716		-		-6,020
Increase (decrease) in cash and cash equivalents			-		-		-		-		49		2,143		-		2,192
Cash and cash equivalents, beginning of year			-		-		-		-		336		1,382		-		1,718
Cash and cash equivalents, end of year		$	-	$	-	$	-	$	-	$	385	$	3,525	$	-	$	3,910
Condensed Consolidating Statement of Cash Flows
For the Year Ended December 31, 2013(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Net cash provided by (used in) operating activities	$	-600	$	-3	$	-151	$	-94	$	-1,102	$	16,110	$	-	$	14,160
Investing Activities:
	Net transactions with affiliates		66		3		2,248		332		-470		-2,179		-		-
	Capital expenditures		-7		-		-		-		-		-6,589		-		-6,596
	Cash paid for intangible assets		-4		-		-		-		-		-1,005		-		-1,009
	Acquisitions and construction of real estate properties		-		-		-		-		-		-1,904		-		-1,904
	Acquisitions, net of cash acquired		-		-		-		-		-		-99		-		-99
	Proceeds from sales of businesses and investments		-		-		-		-		2		1,081		-		1,083
	Return of capital from investees		-		-		-		-		128		21		-		149
	Purchases of investments		-11		-		-		-		-3		-1,209		-		-1,223
	Other		-		-		-		-		-20		105		-		85
	Net cash provided by (used in) investing activities		44		3		2,248		332		-363		-11,778		-		-9,514
Financing Activities:
	Proceeds from (repayments of) short-term borrowings, net		1,349		-		-		-		-		-4		-		1,345
	Proceeds from borrowings		2,933		-		-		-		-		-		-		2,933
	Repurchases and repayments of debt		-		-		-2,097		-238		-88		-21		-		-2,444
	Repurchases and retirements of common stock		-2,000		-		-		-		-		-		-		-2,000
	Dividends paid		-1,964		-		-		-		-		-		-		-1,964
	Issuances of common stock		40		-		-		-		-		-		-		40
	Purchase of NBCUniversal noncontrolling common equity interest		-		-		-		-		-3,200		-7,561		-		-10,761
	Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock		-		-		-		-		-		-215		-		-215
	Settlement of Station Venture liability		-		-		-		-		-		-602		-		-602
	Other		198		-		-		-		-40		-369		-		-211
	Net cash provided by (used in) financing activities		556		-		-2,097		-238		-3,328		-8,772		-		-13,879
Increase (decrease) in cash and cash equivalents			-		-		-		-		-4,793		-4,440		-		-9,233
Cash and cash equivalents, beginning of year			-		-		-		-		5,129		5,822		-		10,951
Cash and cash equivalents, end of year		$	-	$	-	$	-	$	-	$	336	$	1,382	$	-	$	1,718
Condensed Consolidating Statement of Cash Flows
For the Year Ended December 31, 2012(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Net cash provided by (used in) operating activities	$	-362	$	-7	$	-177	$	-114	$	-1,347	$	16,861	$	-	$	14,854
Investing Activities:
	Net transactions with affiliates		3,845		206		177		667		4,850		-9,745		-		-
	Capital expenditures		-10		-		-		-		-		-5,704		-		-5,714
	Cash paid for intangible assets		-6		-		-		-		-		-917		-		-923
	Acquisitions, net of cash acquired		-		-		-		-		-		-90		-		-90
	Proceeds from sales of businesses and investments		-		-		-		-		-		3,102		-		3,102
	Return of capital from investees		-		-		-		-		-		2,362		-		2,362
	Purchases of investments		-		-		-		-		-19		-278		-		-297
	Other		-		3		-		-		-22		93		-		74
	Net cash provided by (used in) investing activities		3,829		209		177		667		4,809		-11,177		-		-1,486
Financing Activities:
	Proceeds from (repayments of) short-term borrowings, net		-1		-		-		-		-550		7		-		-544
	Proceeds from borrowings		2,536		-		-		-		1,995		13		-		4,544
	Repurchases and repayments of debt		-1,726		-202		-		-553		-2		-398		-		-2,881
	Repurchases and retirements of common stock		-3,000		-		-		-		-		-		-		-3,000
	Dividends paid		-1,608		-		-		-		-		-		-		-1,608
	Issuances of common stock		233		-		-		-		-		-		-		233
	Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock		-		-		-		-		-		-691		-		-691
	Other		99		-		-		-		-14		-175		-		-90
	Net cash provided by (used in) financing activities		-3,467		-202		-		-553		1,429		-1,244		-		-4,037
Increase (decrease) in cash and cash equivalents			-		-		-		-		4,891		4,440		-		9,331
Cash and cash equivalents, beginning of year			-		-		-		-		238		1,382		-		1,620
Cash and cash equivalents, end of year		$	-	$	-	$	-	$	-	$	5,129	$	5,822	$	-	$	10,951

Schedule_II_Valuation_and_Qual

Schedule II Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	Comcast Corporation and Subsidiaries
	Schedule II — Valuation and Qualifying Accounts
	Year ended December 31, 2014, 2013 and 2012
	Year Ended December 31 (in millions)			Balance at Beginning of Year		Additions Charged to Costs and Expenses(a)		Deductions from Reserves(a)		Balance at End of Year
	2014
		Allowance for doubtful accounts	$	221	$	162	$	178	$	205
		Allowance for returns and customer incentives		375		932		948		359
		Valuation allowance on deferred tax assets		405		33		63		375
	2013
		Allowance for doubtful accounts	$	198	$	317	$	294	$	221
		Allowance for returns and customer incentives		307		811		743		375
		Valuation allowance on deferred tax assets		355		71		21		405
	2012
		Allowance for doubtful accounts	$	202	$	293	$	297	$	198
		Allowance for returns and customer incentives		425		663		781		307
		Valuation allowance on deferred tax assets		297		61		3		355
	(a) Additions and deductions related to allowance for returns and customer incentives include amounts for distribution on behalf of third parties. Additions and deductions related to allowance for returns and customer incentives for the years ended December 31, 2013 and 2012 also reflect corrections to change amounts that were previously recorded net.
NBCUniversal Media, LLC [Member]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	NBCUniversal Media, LLC
	Schedule II — Valuation and Qualifying Accounts
	Year ended December 31, 2014, 2013 and 2012
	Year Ended December 31 (in millions)			Balance at Beginning of Year		Additions Charged to Costs and Expenses(a)		Deductions from Reserves(a)		Balance at End of Year
	2014
		Allowance for doubtful accounts	$	65	$	11	$	16	$	60
		Allowance for returns and customer incentives		372		930		946		356
		Valuation allowance on deferred tax assets		60		33		6		87
	2013
		Allowance for doubtful accounts	$	46	$	33	$	14	$	65
		Allowance for returns and customer incentives		307		808		743		372
		Valuation allowance on deferred tax assets		73		8		21		60
	2012
		Allowance for doubtful accounts	$	34	$	19	$	7	$	46
		Allowance for returns and customer incentives		425		663		781		307
		Valuation allowance on deferred tax assets		53		23		3		73
	(a) Additions and deductions related to allowance for returns and customer incentives include amounts for distribution on behalf of third parties. Additions and deductions related to allowance for returns and customer incentives for the years ended December 31, 2013 and 2012 also reflect corrections to change amounts that were previously recorded net.

Accounting_Policies_Policy

Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2014
Basis of Presentation	Basis of Presentation
	The accompanying consolidated financial statements include all entities in which we have a controlling voting interest (“subsidiaries”) and variable interest entities (“VIEs”) required to be consolidated in accordance with generally accepted accounting principles in the United States (“GAAP”).
Foreign Currency Translation	We translate assets and liabilities of our foreign subsidiaries where the functional currency is the local currency, primarily the euro and the British pound, into U.S. dollars at the exchange rate as of the balance sheet date and translate revenue and expenses using average monthly exchange rates. The related translation adjustments are recorded as a component of accumulated other comprehensive income (loss). Any foreign currency transaction gains and losses are included in our consolidated statement of income.
Cash Equivalents	Cash Equivalents
	The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased.
Use of Estimates	Our consolidated financial statements are prepared in accordance with GAAP, which requires us to select accounting policies, including in certain cases industry-specific policies, and make estimates that affect the reported amount of assets, liabilities, revenue and expenses, and the related disclosure of contingent assets and contingent liabilities. Actual results could differ from these estimates. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements:
	valuation and impairment testing of cable franchise rights (see Note 9)
	film and television costs (see Note 6)
	income taxes (see Note 15)
	In addition, the following accounting policies are specific to the industries in which we operate:
	capitalization and amortization of film and television costs (see Note 6)
	installation costs for connecting customers to our cable systems (see Note 8)
	Information on our other accounting policies or methods related to our consolidated financial statements are included, where applicable, in their respective footnotes that follow. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes.
Film And Television Costs	Capitalization of Film and Television Costs
	We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expense. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes such costs in the same ratio as the associated ultimate revenue. Estimates of total revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television costs, including acquired film and television libraries, are stated at the lower of unamortized cost or fair value. We do not capitalize costs related to the distribution of a film to movie theaters or the licensing or sale of a film or television production, which are primarily costs associated with the marketing and distribution of film and television programming.
	In determining the estimated lives and method of amortization of acquired film and television libraries, we generally use the method and the life that most closely follow the undiscounted cash flows over the estimated life of the asset.
	Upon the occurrence of an event or a change in circumstance that was known or knowable as of the balance sheet date and that indicates the fair value of a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value.
	We enter into cofinancing arrangements with third parties to jointly finance or distribute certain of our film productions. Cofinancing arrangements can take various forms, but in most cases involve the grant of an economic interest in a film to an investor. The number of investors and the terms of these arrangements can vary, although investors generally assume full risk for the portion of the film acquired in these arrangements. We account for the proceeds received from a third-party investor under these arrangements as a reduction to our capitalized film costs. In these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expense to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life.
	We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is available for use. We amortize capitalized programming costs as the associated programs are broadcast. We amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated total remaining revenue or under the terms of the contract.
	Acquired programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Acquired programming used in our Cable Networks segment is primarily tested on a channel basis for impairment, whereas acquired programming used in our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expense.
Investments	Fair Value Method
	We classify publicly traded investments that are not accounted for under the equity method as available-for-sale (“AFS”) or trading securities and record them at fair value. For AFS securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of other comprehensive income (loss), except when we consider declines in value to be other than temporary. For trading securities, we record unrealized gains or losses resulting from changes in fair value between measurement dates as a component of investment income (loss), net. We recognize realized gains and losses associated with our fair value method investments using the specific identification method. We classify the cash flows related to purchases of and proceeds from the sale of trading securities based on the nature of the securities and the purpose for which they were acquired.
	Equity Method
	We use the equity method to account for investments in which we have the ability to exercise significant influence over the investee’s operating and financial policies or where we hold significant partnership or LLC interests. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share of the investee’s net income or loss after the date of investment, (2) amortization of the recorded investment that exceeds our share of the book value of the investee’s net assets, (3) additional contributions made and dividends received, and (4) impairments resulting from other-than-temporary declines in fair value. For some investments, we record our share of the investee’s net income or loss one quarter in arrears due to the timing of our receipt of such information. Gains or losses on the sale of equity method investments are recorded to other income (expense), net. If an equity method investee were to issue additional securities that would change our proportionate share of the entity, we would recognize the change, if any, as a gain or loss in our consolidated statement of income.
	Cost Method
	We use the cost method to account for investments not accounted for under the fair value method or the equity method.
	Impairment Testing of Investments
	We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. For our nonpublic investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. If an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. For our AFS and cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), net.
Property and Equipment	Property and equipment are stated at cost. We capitalize improvements that extend asset lives and expense repairs and maintenance costs as incurred. We record depreciation using the straight-line method over the asset’s estimated useful life. For assets that are sold or retired, we remove the applicable cost and accumulated depreciation and, unless the gain or loss on disposition is presented separately, we recognize it as a component of depreciation expense.
	We capitalize the costs associated with the construction of and improvements to our cable transmission and distribution facilities, costs associated with acquiring and deploying new customer premise equipment, and costs associated with installation of our services in accordance with accounting guidance related to cable television companies. Costs capitalized include all direct labor and materials, as well as various indirect costs. All costs incurred in connection with subsequent disconnects and reconnects are expensed as they are incurred.
	We evaluate the recoverability of our property and equipment whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of depreciation expense.
Goodwill and Intangible Assets	We assess the recoverability of our goodwill annually, or more frequently whenever events or substantive changes in circumstances indicate that the carrying amount of a reporting unit may exceed its fair value. We test goodwill for impairment at the reporting unit level. To determine our reporting units, we evaluate the components one level below the segment level and we aggregate the components if they have similar economic characteristics. As a result of this assessment, our reporting units are the same as our five reportable segments. We evaluate the determination of our reporting units used to test for impairment periodically or whenever events or substantive changes in circumstances occur. The assessment of recoverability may first consider qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. The quantitative assessment considers if the carrying amount of a reporting unit exceeds its fair value, in which case an impairment charge is recorded to the extent the carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
	Indefinite-Lived Intangible Assets
	Indefinite-lived intangible assets consist primarily of our cable franchise rights, as well as trade names and FCC licenses. Our cable franchise rights represent the values we attributed to agreements with state and local authorities that allow access to homes and businesses in cable service areas acquired in business combinations. We do not amortize our cable franchise rights because we have determined that they meet the definition of indefinite-lived intangible assets since there are no legal, regulatory, contractual, competitive, economic or other factors which limit the period over which these rights will contribute to our cash flows. We reassess this determination periodically or whenever events or substantive changes in circumstances occur. Costs we incur in negotiating and renewing cable franchise agreements are included in other intangible assets and are generally amortized on a straight-line basis over the term of the franchise agreement.
	We assess the recoverability of our cable franchise rights and other indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. Our three Cable Communications divisions represent the unit of account we use to test for impairment for our cable franchise rights. We evaluate the unit of account used to test for impairment of our cable franchise rights and other indefinite-lived intangible assets periodically or whenever events or substantive changes in circumstances occur to ensure impairment testing is performed at an appropriate level. The assessment of recoverability may first consider qualitative factors to determine whether it is more likely than not that the fair value of an indefinite-lived intangible asset is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. When performing a quantitative assessment, we estimate the fair value of our cable franchise rights and other indefinite-lived intangible assets primarily based on a discounted cash flow analysis that involves significant judgment. When analyzing the fair values indicated under the discounted cash flow models, we also consider multiples of operating income before depreciation and amortization generated by the underlying assets, current market transactions, and profitability information. If the fair value of our cable franchise rights or other indefinite-lived intangible assets were less than the carrying amount, we would recognize an impairment charge for the difference between the estimated fair value and the carrying value of the assets. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any material impairment charges in any of the periods presented.
	Finite-Lived Intangible Assets
	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, software, cable franchise renewal costs, contractual operating rights, and intellectual property rights. Our finite-lived intangible assets are amortized primarily on a straight-line basis over their estimated useful life or the term of the associated agreement.
	We capitalize direct development costs associated with internal-use software, including external direct costs of material and services and payroll costs for employees devoting time to these software projects. We also capitalize costs associated with the purchase of software licenses. We include these costs in other intangible assets and amortize them on a straight-line basis over a period not to exceed five years. We expense maintenance and training costs, as well as costs incurred during the preliminary stage of a project, as they are incurred. We capitalize initial operating system software costs and amortize them over the life of the associated hardware.
	We evaluate the recoverability of our finite-lived intangible assets whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
Asset Retirement Obligations	Asset Retirement Obligations
	Certain of our cable franchise agreements and lease agreements contain provisions requiring us to restore facilities or remove property in the event that the franchise or lease agreement is not renewed. We expect to continually renew our cable franchise agreements and therefore cannot reasonably estimate any liabilities associated with such agreements. A remote possibility exists that franchise agreements could be terminated unexpectedly, which could result in us incurring significant expense in complying with restoration or removal provisions. The disposal obligations related to our properties are not material to our consolidated financial statements. We do not have any significant liabilities related to asset retirements recorded in our consolidated financial statements.
Revenue Recognition	Revenue Recognition
	Cable Communications Segment
	Our Cable Communications segment generates revenue primarily from subscriptions to our video, high-speed Internet and voice services (“cable services”) and from the sale of advertising. We recognize revenue from cable services as each service is provided. Customers are typically billed in advance on a monthly basis based on the services and features they receive and the type of equipment they use. We manage credit risk by screening applicants through the use of internal customer information, identification verification tools and credit bureau data. If a customer’s account is delinquent, various measures are used to collect outstanding amounts, including termination of the customer’s cable services. Since installation revenue obtained from the connection of customers to our cable systems is less than the related direct selling costs, we recognize revenue as connections are completed.
	As part of our distribution agreements with cable networks, we generally receive an allocation of scheduled advertising time on cable networks that our Spotlight business sells to local, regional and national advertisers. We recognize advertising revenue when the advertising is aired. In most cases, the available advertising units are sold by our sales force. In some cases, we work with representation firms as an extension of our sales force to sell a portion of the advertising units allocated to us. We also represent the advertising sales efforts of other multichannel video providers in some markets. Since we are acting as the principal in these arrangements, we report the advertising that is sold as revenue and the fees paid to representation firms and multichannel video providers as other operating and administrative expenses.
	Revenue earned from other sources, such as our home security and automation services, is recognized when services are provided or events occur. Under the terms of our cable franchise agreements, we are generally required to pay to the cable franchising authority an amount based on our gross video revenue. We normally pass these fees through to our cable services customers and classify the fees as a component of revenue with the corresponding costs included in other operating and administrative expenses.
	Cable Networks and Broadcast Television Segments
	Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to multichannel video providers, from the sale of advertising on our cable networks and related digital media properties, from the licensing of our owned programming through distribution to subscription video on demand services and various other distribution platforms, and from the sale of our owned programming electronically through digital distributors such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and related digital media properties, from the licensing of our owned programming through various distribution platforms, including to cable and broadcast networks and to subscription video on demand services, and from fees received under retransmission consent agreements. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution.
	Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which commercials are aired or viewed. In some instances, we guarantee viewer ratings for the commercials. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We record revenue from the licensing of our owned programming when the content is available for use by the licensee, and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed.
	Filmed Entertainment Segment
	Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of our owned and acquired films through various distribution platforms, and from the sale of our owned and acquired films on standard-definition video discs and Blu-ray discs (together, “DVDs”) and electronically through digital distributors. Our Filmed Entertainment segment also generates revenue from producing and licensing live stage plays, from the distribution of filmed entertainment produced by third parties, and from a movie ticketing and entertainment business. We recognize <>revenue from the distribution of films to movie theaters when the films are exhibited. We record revenue from the licensing of a film when the film is available for use by the licensee, and when certain other conditions are met. We recognize revenue from DVD sales, net of estimated returns and customer incentives, on the date that DVDs are delivered to and made available for sale by retailers.
	Theme Parks Segment
	Our Theme Parks segment generates revenue primarily from theme park attendance and per capita spending at our Universal theme parks in Orlando, Florida and Hollywood, California, as well as from licensing and other fees. We recognize <>revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the annual period following the initial activation date.
Cable Communications Programming Expenses	Cable Communications Programming Expenses
	Cable Communications programming expenses are the fees we pay to license the programming we distribute to our video customers. Programming is acquired for distribution to our video customers, generally under multiyear distribution agreements, with rates typically based on the number of customers that receive the programming, channel positioning and the extent of distribution. From time to time, these contracts expire and programming continues to be provided under interim arrangements while the parties negotiate new contractual terms, sometimes with effective dates that affect prior periods. While payments are typically made under the prior contract’s terms, the amount of programming expenses recorded during these interim arrangements is based on our estimates of the ultimate contractual terms expected to be negotiated. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution.
	When our Cable Communications segment receives incentives from cable networks for the licensing of their programming, we defer a portion of these incentives, which are included in other current and noncurrent liabilities, and recognize them over the term of the contract as a reduction to programming expenses.
Advertising Expenses	Advertising Expenses
	Advertising costs are expensed as incurred.
Share-Based Compensation	As of December 31, 2014, substantially all of our stock options outstanding were net settled stock options. Net settled stock options, as opposed to stock options exercised with a cash payment, result in fewer shares being issued and no cash proceeds being received by us when the options are exercised. Our share-based compensation primarily consists of awards of stock options and RSUs to certain employees and directors as part of our approach to long-term incentive compensation. Awards generally vest over a period of 5 years and in the case of stock options, have a 10 year term. Additionally, through our employee stock purchase plans, employees are able to purchase shares of Comcast Class A common stock at a discount through payroll deductions.
	The cost associated with our share-based compensation is based on an award’s estimated fair value at the date of grant and is recognized over the period in which any related services are provided. We use the Black-Scholes option pricing model to estimate the fair value of stock option awards. RSUs are valued based on the closing price of our Class A common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period. The table below presents the weighted-average fair value on the date of grant of RSUs and Class A common stock options awarded under our various plans and the related weighted-average valuation assumptions.
Postretirement and Pension Benefits	All of our postretirement benefit plans are unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for our postretirement benefit plans is determined using certain assumptions, including the discount rate.
	NBCUniversal
	NBCUniversal sponsors various qualified and nonqualified defined benefit plans for domestic employees for which future benefits have been frozen. We ceased to recognize service costs associated with these defined benefit plans following the date on which future benefits were frozen. The expense we recognize for our defined benefit plans is determined using certain assumptions, including the discount rate and the expected long-term rate of return on plan assets. We recognize the funded or unfunded status of our defined benefit plans as an asset or liability in our consolidated balance sheet and recognize changes in the funded status in the year in which the changes occur through accumulated other comprehensive income (loss). In addition to the defined benefit plans it sponsors, NBCUniversal is also obligated to reimburse GE for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of the NBCUniversal transaction in 2011.
Income Taxes	We base our provision for income taxes on our current period income, changes in our deferred income tax assets and liabilities, income tax rates, changes in estimates of our uncertain tax positions, and tax planning opportunities available in the jurisdictions in which we operate. We recognize deferred tax assets and liabilities when there are temporary differences between the financial reporting basis and tax basis of our assets and liabilities and for the expected benefits of using net operating loss carryforwards. When a change in the tax rate or tax law has an impact on deferred taxes, we apply the change based on the years in which the temporary differences are expected to reverse. We record the change in our consolidated financial statements in the period of enactment.
	Income tax consequences that arise in connection with a business combination include identifying the tax basis of assets and liabilities acquired and any contingencies associated with uncertain tax positions assumed or resulting from the business combination. Deferred tax assets and liabilities related to temporary differences of an acquired entity are recorded as of the date of the business combination and are based on our estimate of the ultimate tax basis that will be accepted by the various taxing authorities. We record liabilities for contingencies associated with prior tax returns filed by the acquired entity based on criteria set forth in the appropriate accounting guidance. We adjust the deferred tax accounts and the liabilities periodically to reflect any revised estimated tax basis and any estimated settlements with the various taxing authorities. The effects of these adjustments are recorded to income tax expense.
	From time to time, we engage in transactions in which the tax consequences may be subject to uncertainty. In these cases, we evaluate our tax positions using the recognition threshold and the measurement attribute in accordance with the accounting guidance related to uncertain tax positions. Examples of these transactions include business acquisitions and dispositions, including consideration paid or received in connection with these transactions, certain financing transactions, and the allocation of income among state and local taxing jurisdictions. Significant judgment is required in assessing and estimating the tax consequences of these transactions. We determine whether it is more likely than not that a tax position will be sustained on examination, including the resolution of any related appeals or litigation processes, based on the technical merits of the position. A tax position that meets the more-likely-than-not recognition threshold is measured to determine the amount of benefit to be recognized in our consolidated financial statements. We classify interest and penalties, if any, associated with our uncertain tax positions as a component of income tax expense.
Derivative Financial Instruments	Derivative Financial Instruments
	We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in interest rates, foreign exchange rates and equity prices. Our objective is to manage the financial and operational exposure arising from these risks by offsetting gains and losses on the underlying exposures with gains and losses on the derivatives used to economically hedge them.
	Our derivative financial instruments are recorded in our consolidated balance sheet at fair value. See Note 7 for additional information on the derivative component of our prepaid forward sale agreements. The impact of other derivative financial instruments on our consolidated financial statements was not material for all periods presented.
	The derivative component of the prepaid forward sale agreements are equity derivative financial instruments embedded in the related contracts, which we use to manage our exposure to and benefits from price fluctuations in the common stock of the related investments. For these derivative financial instruments, we separate the derivative component from the host contract and record the change in its value each period to investment income (loss), net.
Earnings Per Share	Diluted earnings per common share attributable to Comcast Corporation shareholders (“diluted EPS”) considers the impact of potentially dilutive securities using the treasury stock method. Our potentially dilutive securities include potential common shares related to our stock options and our restricted share units (“RSUs”). Diluted EPS excludes the impact of potential common shares related to our stock options in periods in which the combination of the option exercise price and the associated unrecognized compensation expense is greater than the average market price of our Class A common stock or our Class A Special common stock, as applicable.
	The amount of potential common shares related to our share-based compensation plans that were excluded from diluted EPS because their effect would have been antidilutive was not material for 2014, 2013 and 2012.
Fair Value of Financial Instruments	The accounting guidance related to financial assets and financial liabilities (“financial instruments”) establishes a hierarchy that prioritizes fair value measurements based on the types of inputs used for the various valuation techniques (market approach, income approach and cost approach). The levels of the hierarchy are described below.
	Level 1: Consists of financial instruments whose values are based on quoted market prices for identical financial instruments in an active market.
	Level 2: Consists of financial instruments that are valued using models or other valuation methodologies. These models use inputs that are observable either directly or indirectly. Level 2 inputs include (1) quoted prices for similar assets or liabilities in active markets, (2) quoted prices for identical or similar assets or liabilities in markets that are not active, (3) pricing models whose inputs are observable for substantially the full term of the financial instrument and (4) pricing models whose inputs are derived primarily from or corroborated by observable market data through correlation or other means for substantially the full term of the financial instrument.
	Level 3: Consists of financial instruments whose values are determined using pricing models that use significant inputs that are primarily unobservable, discounted cash flow methodologies or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.
	Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial instruments and their classification within the fair value hierarchy. Financial instruments are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. There have been no changes in the classification of any financial instruments within the fair value hierarchy in the periods presented. Our financial instruments that are accounted for at fair value on a recurring basis are presented in the table below.
NBCUniversal Media, LLC [Member]
Basis of Presentation	The accompanying consolidated financial statements include all entities in which we have a controlling voting interest (“subsidiaries”) and variable interest entities (“VIEs”) required to be consolidated in accordance with generally accepted accounting principles in the United States (“GAAP”). Transactions between NBCUniversal and both Comcast and Comcast’s consolidated subsidiaries are reflected in these consolidated financial statements and disclosed as related party transactions when material.
Foreign Currency Translation	We translate assets and liabilities of our foreign subsidiaries where the functional currency is the local currency, primarily the euro and the British pound, into U.S. dollars at the exchange rate as of the balance sheet date and translate revenue and expenses using average monthly exchange rates. The related translation adjustments are recorded as a component of accumulated other comprehensive income (loss). Any foreign currency transaction gains and losses are included in our consolidated statement of income.
Cash Equivalents	Cash Equivalents
	The carrying amounts of our cash equivalents approximate their fair values. Our cash equivalents consist primarily of money market funds and U.S. government obligations, as well as commercial paper and certificates of deposit with maturities of three months or less when purchased.
Use of Estimates	Our consolidated financial statements are prepared in accordance with GAAP, which requires us to select accounting policies, including in certain cases industry-specific policies, and make estimates that affect the reported amount of assets, liabilities, revenue and expenses, and the related disclosure of contingent assets and contingent liabilities. Actual results could differ from these estimates. We believe that the judgments and related estimates for the following items are critical in the preparation of our consolidated financial statements:
	revenue recognition (see below)
	film and television costs (see Note 6)
	goodwill and intangible assets (see Note 9)
	fair value of contractual obligations (see Note 11)
	In addition, the following accounting policies are specific to the industries in which we operate:
	capitalization and amortization of film and television costs (see Note 6)
	Information on our other accounting policies or methods related to our consolidated financial statements are included, where applicable, in their respective footnotes that follow. Below is a discussion of accounting policies and methods used in our consolidated financial statements that are not presented within other footnotes.
Film And Television Costs	Capitalization of Film and Television Costs
	We capitalize film and television production costs, including direct costs, production overhead, print costs, development costs and interest. We amortize capitalized film and television production costs, including acquired libraries, and accrue costs associated with participation and residual payments to programming and production expense. We generally record the amortization and the accrued costs using the individual film forecast computation method, which amortizes such costs in the same ratio as the associated ultimate revenue. Estimates of total revenue and total costs are based on anticipated release patterns, public acceptance and historical results for similar productions. Unamortized film and television costs, including acquired film and television libraries, are stated at the lower of unamortized cost or fair value. We do not capitalize costs related to the distribution of a film to movie theaters or the licensing or sale of a film or television production, which are primarily costs associated with the marketing and distribution of film and television programming.
	In determining the estimated lives and method of amortization of acquired film and television libraries, we generally use the method and the life that most closely follow the undiscounted cash flows over the estimated life of the asset.
	Upon the occurrence of an event or a change in circumstance that was known or knowable as of the balance sheet date and that indicates the fair value of a film is less than its unamortized costs, we determine the fair value of the film and record an impairment charge for the amount by which the unamortized capitalized costs exceed the film’s fair value.
	We enter into cofinancing arrangements with third parties to jointly finance or distribute certain of our film productions. Cofinancing arrangements can take various forms, but in most cases involve the grant of an economic interest in a film to an investor. The number of investors and the terms of these arrangements can vary, although investors generally assume full risk for the portion of the film acquired in these arrangements. We account for the proceeds received from a third-party investor under these arrangements as a reduction to our capitalized film costs. In these arrangements, the investor owns an undivided copyright interest in the film, and therefore in each period we record either a charge or a benefit to programming and production expense to reflect the estimate of the third-party investor’s interest in the profit or loss of the film. The estimate of the third-party investor’s interest in the profit or loss of a film is determined using the ratio of actual revenue earned to date to the ultimate revenue expected to be recognized over the film’s useful life.
	We capitalize the costs of programming content that we license but do not own, including rights to multiyear, live-event sports programming, at the earlier of when payments are made for the programming or when the license period begins and the content is available for use. We amortize capitalized programming costs as the associated programs are broadcast. We amortize multiyear, live-event sports programming rights using the ratio of the current period revenue to the estimated total remaining revenue or under the terms of the contract.
	Acquired programming costs are recorded at the lower of unamortized cost or net realizable value on a program by program, package, channel or daypart basis. A daypart is an aggregation of programs broadcast during a particular time of day or programs of a similar type. Acquired programming used in our Cable Networks segment is primarily tested on a channel basis for impairment, whereas acquired programming used in our Broadcast Television segment is tested on a daypart basis. If we determine that the estimates of future cash flows are insufficient or if there is no plan to broadcast certain programming, we recognize an impairment charge to programming and production expense.
Investments	Equity Method
	We use the equity method to account for investments in which we have the ability to exercise significant influence over the investee’s operating and financial policies or where we hold significant partnership or LLC interests. Equity method investments are recorded at cost and are adjusted to recognize (1) our proportionate share of the investee’s net income or loss after the date of investment, (2) amortization of the recorded investment that exceeds our share of the book value of the investee’s net assets, (3) additional contributions made and dividends received, and (4) impairments resulting from other-than-temporary declines in fair value. Gains or losses on the sale of equity method investments are recorded to other income (expense), net. If an equity method investee were to issue additional securities that would change our proportionate share of the entity, we would recognize the change, if any, as a gain or loss in our consolidated statement of income.
	Impairment Testing of Investments
	We review our investment portfolio each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that would be considered other than temporary. For our nonpublic investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. If an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. For our available-for-sale securities and cost method investments, we record the impairment to investment income (loss), net. For our equity method investments, we record the impairment to other income (expense), net.
Property and Equipment	Property and equipment are stated at cost. We capitalize improvements that extend asset lives and expense repairs and maintenance costs as incurred. We record depreciation using the straight-line method over the asset’s estimated useful life. For assets that are sold or retired, we remove the applicable cost and accumulated depreciation and, unless the gain or loss on disposition is presented separately, we recognize it as a component of depreciation expense.
	We evaluate the recoverability of our property and equipment whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of depreciation expense.
Goodwill and Intangible Assets	We assess the recoverability of our goodwill annually, or more frequently whenever events or substantive changes in circumstances indicate that the carrying amount of a reporting unit may exceed its fair value. We test goodwill for impairment at the reporting unit level. To determine our reporting units, we evaluate the components one level below the segment level and we aggregate the components if they have similar economic characteristics. As a result of this assessment, our reporting units are the same as our four reportable segments. We evaluate the determination of our reporting units used to test for impairment periodically or whenever events or substantive changes in circumstances occur. The assessment of recoverability may first consider qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. The quantitative assessment considers if the carrying amount of a reporting unit exceeds its fair value, in which case an impairment charge is recorded to the extent the carrying amount of the reporting unit’s goodwill exceeds its implied fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
	Indefinite-Lived Intangible Assets
	Indefinite-lived intangible assets consist of trade names and FCC licenses. We assess the recoverability of our indefinite-lived intangible assets annually, or more frequently whenever events or substantive changes in circumstances indicate that the assets might be impaired. We evaluate the unit of account used to test for impairment of our indefinite-lived intangible assets periodically or whenever events or substantive changes in circumstances occur to ensure impairment testing is performed at an appropriate level. The assessment of recoverability may first consider qualitative factors to determine whether it is more likely than not that the fair value of an indefinite-lived intangible asset is less than its carrying amount. A quantitative assessment is performed if the qualitative assessment results in a more-likely-than-not determination or if a qualitative assessment is not performed. When performing a quantitative assessment, we estimate the fair value of our indefinite-lived intangible assets primarily based on a discounted cash flow analysis that involves significant judgment. When analyzing the fair values indicated under the discounted cash flow models, we also consider multiples of operating income before depreciation and amortization generated by the underlying assets, current market transactions, and profitability information. If the fair value of our indefinite-lived intangible assets were less than the carrying amount, we would recognize an impairment charge for the difference between the estimated fair value and the carrying value of the assets. Unless presented separately, the impairment charge is included as a component of amortization expense. We did not recognize any material impairment charges in any of the periods presented.
	Finite-Lived Intangible Assets
	Finite-lived intangible assets are subject to amortization and consist primarily of customer relationships acquired in business combinations, intellectual property rights and software. Our finite-lived intangible assets are amortized primarily on a straight-line basis over their estimated useful life or the term of the associated agreement.
	We capitalize direct development costs associated with internal-use software, including external direct costs of material and services and payroll costs for employees devoting time to these software projects. We also capitalize costs associated with the purchase of software licenses. We include these costs in intangible assets and amortize them on a straight-line basis over a period not to exceed five years. We expense maintenance and training costs, as well as costs incurred during the preliminary stage of a project, as they are incurred. We capitalize initial operating system software costs and amortize them over the life of the associated hardware.
	We evaluate the recoverability of our finite-lived intangible assets whenever events or substantive changes in circumstances indicate that the carrying amount may not be recoverable. The evaluation is based on the cash flows generated by the underlying asset groups, including estimated future operating results, trends or other determinants of fair value. If the total of the expected future undiscounted cash flows were less than the carrying amount of the asset group, we would recognize an impairment charge to the extent the carrying amount of the asset group exceeded its estimated fair value. Unless presented separately, the impairment charge is included as a component of amortization expense.
Revenue Recognition	Revenue Recognition
	Cable Networks and Broadcast Television Segments
	Our Cable Networks segment generates revenue primarily from the distribution of our cable network programming to multichannel video providers, from the sale of advertising on our cable networks and related digital media properties, from the licensing of our owned programming through distribution to subscription video on demand services and various other distribution platforms, and from the sale of our owned programming electronically through digital distributors such as iTunes. Our Broadcast Television segment generates revenue primarily from the sale of advertising on our broadcast networks, owned local broadcast television stations and related digital media properties, from the licensing of our owned programming through various distribution platforms, including to cable and broadcast networks and to subscription video on demand services, and from fees received under retransmission consent agreements. We recognize revenue from distributors as programming is provided, generally under multiyear distribution agreements. From time to time, the distribution agreements expire while programming continues to be provided to the distributor based on interim arrangements while the parties negotiate new contract terms. Revenue recognition is generally limited to current payments being made by the distributor, typically under the prior contract terms, until a new contract is negotiated, sometimes with effective dates that affect prior periods. Differences between actual amounts determined upon resolution of negotiations and amounts recorded during these interim arrangements are recorded in the period of resolution.
	Advertising revenue for our Cable Networks and Broadcast Television segments is recognized in the period in which commercials are aired or viewed. In some instances, we guarantee viewer ratings for the commercials. To the extent there is a shortfall in the ratings that were guaranteed, a portion of the revenue is deferred until the shortfall is settled, primarily by providing additional advertising units. We record revenue from the licensing of our owned programming when the content is available for use by the licensee, and when certain other conditions are met. When license fees include advertising time, we recognize the component of revenue associated with the advertisements when they are aired or viewed.
	Filmed Entertainment Segment
	Our Filmed Entertainment segment generates revenue primarily from the worldwide distribution of our produced and acquired films for exhibition in movie theaters, from the licensing of our owned and acquired films through various distribution platforms, and from the sale of our owned and acquired films on standard-definition video discs and Blu-ray discs (together, “DVDs”) and electronically through digital distributors. Our Filmed Entertainment segment also generates revenue from producing and licensing live stage plays, from the distribution of filmed entertainment produced by third parties, and from a movie ticketing and entertainment business. We recognize <>revenue from the distribution of films to movie theaters when the films are exhibited. We record revenue from the licensing of a film when the film is available for use by the licensee, and when certain other conditions are met. We recognize revenue from DVD sales, net of estimated returns and customer incentives, on the date that DVDs are delivered to and made available for sale by retailers.
	Theme Parks Segment
	Our Theme Parks segment generates revenue primarily from theme park attendance and per capita spending at our Universal theme parks in Orlando, Florida and Hollywood, California, as well as from licensing and other fees. We recognize <>revenue from advance theme park ticket sales when the tickets are used. For annual passes, we recognize revenue on a straight-line basis over the annual period following the initial activation date.
Advertising Expenses	Advertising Expenses
	Advertising costs are expensed as incurred.
Share-Based Compensation	Comcast maintains share-based compensation plans that primarily consist of awards of stock options and RSUs to certain employees and directors as part of its approach to long-term incentive compensation. Awards generally vest over a period of 5 years and in the case of stock options, have a 10 year term. Additionally, through its employee stock purchase plans, employees are able to purchase shares of Comcast Class A common stock at a discount through payroll deductions. Certain of our employees participate in these plans and the expense associated with their participation is settled in cash with Comcast.
	The cost associated with Comcast’s share-based compensation is based on an award’s estimated fair value at the date of grant and is recognized over the period in which any related services are provided. Comcast uses the Black-Scholes option pricing model to estimate the fair value of stock option awards. RSUs are valued based on the closing price of Comcast Class A common stock on the date of grant and are discounted for the lack of dividends, if any, during the vesting period.
Postretirement and Pension Benefits	All of our postretirement benefit plans are unfunded and substantially all of our postretirement benefit obligations are recorded to noncurrent liabilities. The expense we recognize for our postretirement benefit plans is determined using certain assumptions, including the discount rate.
	Pension Plans
	We sponsor various qualified and nonqualified defined benefit plans for domestic employees for which future benefits have been frozen. We ceased to recognize service costs associated with these defined benefit plans following the date on which future benefits were frozen. The expense we recognize for our defined benefit plans is determined using certain assumptions, including the discount rate and the expected long-term rate of return on plan assets. We recognize the funded or unfunded status of our defined benefit plans as an asset or liability in our consolidated balance sheet and recognize changes in the funded status in the year in which the changes occur through accumulated other comprehensive income (loss). In addition to the defined benefit plans we sponsor, we are also obligated to reimburse GE for future benefit payments to those participants who were vested in the supplemental pension plan sponsored by GE at the time of the joint venture transaction.
Derivative Financial Instruments	Derivative Financial Instruments
	We use derivative financial instruments to manage our exposure to the risks associated with fluctuations in foreign exchange rates and interest rates. Our objective is to manage the financial and operational exposure arising from these risks by offsetting gains and losses on the underlying exposures with gains and losses on the derivatives used to economically hedge them.
	Our derivative financial instruments are recorded in our consolidated balance sheet at fair value.
Fair Value of Financial Instruments	The accounting guidance related to financial assets and financial liabilities (“financial instruments”) establishes a hierarchy that prioritizes fair value measurements based on the types of inputs used for the various valuation techniques (market approach, income approach and cost approach). Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial instruments and their classification within the fair value hierarchy.
	Our financial instruments that are accounted for at fair value on a recurring basis were not material for all periods presented, except for liabilities associated with our contractual obligations. The fair values of the contractual obligations in the table below are primarily based on certain expected future discounted cash flows, the determination of which involves the use of significant unobservable inputs. As the inputs used are not quoted market prices or observable inputs, we classify these contractual obligations as Level 3 financial instruments.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share
Computation of diluted EPS	Computation of Diluted EPS
				2014					2013					2012
	Year ended December 31 (in millions, except per share data)			Net Income Attributable to Comcast Corporation	Shares		Per Share Amount		Net Income Attributable to Comcast Corporation	Shares		Per Share Amount		Net Income Attributable to Comcast Corporation	Shares		Per Share Amount
	Basic EPS attributable to Comcast Corporation shareholders		$	8,380	2,583	$	3.24	$	6,816	2,625	$	2.6	$	6,203	2,678	$	2.32
	Effect of dilutive securities:
		Assumed exercise or issuance of shares relating to stock plans			37					40					39
	Diluted EPS attributable to Comcast
		Corporation shareholders	$	8,380	2,620	$	3.2	$	6,816	2,665	$	2.56	$	6,203	2,717	$	2.28

Related_Party_Transactions_Tab

Related Party Transactions (Tables) (NBCUniversal Media, LLC [Member])	12 Months Ended
	Dec. 31, 2014
NBCUniversal Media, LLC [Member]
Related Party Transactions Condensed Financial Statements	Consolidated Balance Sheet
	December 31 (in millions)			2014			2013
	Transactions with Comcast and Consolidated Subsidiaries
		Receivables, net		$	229		$	228
		Accounts payable and accrued expenses related to trade creditors		$	47		$	56
		Accrued expenses and other current liabilities		$	8		$	37
		Note payable to Comcast		$	865		$	799
		Other noncurrent liabilities		$	383		$	383
	Consolidated Statement of Income
	Year ended December 31 (in millions)			2014		2013		2012
	Transactions with Comcast and Consolidated Subsidiaries
		Revenue	$	1,315	$	1,262	$	1,228
		Operating costs and expenses	$	-162	$	-190	$	-175
		Other income (expense)	$	-43	$	-	$	-

Film_and_Television_Costs_Tabl

Film and Television Costs (Tables)	12 Months Ended
	Dec. 31, 2014
Film and Television Costs	December 31 (in millions)			2014		2013
	Film Costs:
		Released, less amortization	$	1,371	$	1,630
		Completed, not released		71		70
		In production and in development		1,189		658
				2,631		2,358
	Television Costs:
		Released, less amortization		1,273		1,155
		In production and in development		505		370
				1,778		1,525
	Programming rights, less amortization			2,157		2,039
				6,566		5,922
	Less: Current portion of programming rights			839		928
	Film and television costs		$	5,727	$	4,994
NBCUniversal Media, LLC [Member]
Film and Television Costs	December 31 (in millions)			2014		2013
	Film Costs:
		Released, less amortization	$	1,371	$	1,630
		Completed, not released		71		70
		In production and in development		1,189		658
				2,631		2,358
	Television Costs:
		Released, less amortization		1,273		1,155
		In production and in development		505		370
				1,778		1,525
	Programming rights, less amortization			2,130		2,003
				6,539		5,886
	Less: Current portion of programming rights			825		903
	Film and television costs		$	5,714	$	4,983

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Investment Summary	December 31 (in millions)			2014		2013
	Fair Value Method		$	662	$	4,345
	Equity Method:
		The Weather Channel		335		333
		Hulu		167		187
		Other		517		469
				1,019		989
	Cost Method:
		AirTouch		1,568		1,553
		Other		488		456
				2,056		2,009
	Total investments			3,737		7,343
	Less: Current investments			602		3,573
	Noncurrent investments		$	3,135	$	3,770
Investment Income (Loss), Net	Investment Income (Loss), Net
	Year ended December 31 (in millions)			2014		2013		2012
	Gains on sales and exchanges of investments, net		$	192	$	484	$	30
	Investment impairment losses			-50		-29		-24
	Unrealized gains on securities underlying prepaid forward sale agreements			66		1,601		1,159
	Mark to market adjustments on derivative component of prepaid forward sale
		agreements and indexed debt instruments		-56		-1,604		-1,071
	Interest and dividend income			116		111		119
	Other, net			28		13		6
	Investment income (loss), net		$	296	$	576	$	219
Prepaid Forward Sale Agreements	Prepaid Forward Sale Agreements
	December 31 (in millions)			2014		2013
	Assets:
		Fair value equity securities held as collateral	$	523	$	3,959
	Liabilities:
		Obligations under prepaid forward sale agreements	$	119	$	811
		Derivative component of prepaid forward sale agreements		356		2,800
	Total liabilities		$	475	$	3,611
NBCUniversal Media, LLC [Member]
Investment Summary	December 31 (in millions)			2014		2013
	Fair Value Method		$	10	$	11
	Equity Method:
		The Weather Channel		335		333
		Hulu		167		187
		Other		338		332
				840		852
	Cost Method			32		21
	Total investments		$	882	$	884

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property and Equipment	December 31 (in millions)	Weighted-Average Original Useful LifeAs of December 31, 2014			2014		2013
	Cable distribution system	11	years	$	31,655	$	30,498
	Customer premise equipment	6	years		27,086		25,949
	Other equipment	6	years		7,860		6,826
	Buildings and leasehold improvements	22	years		8,650		8,057
	Land		N/A		1,112		1,084
	Property and equipment, at cost				76,363		72,414
	Less: Accumulated depreciation				45,410		42,574
	Property and equipment, net			$	30,953	$	29,840
NBCUniversal Media, LLC [Member]
Property and Equipment	December 31 (in millions)	Weighted-Average Original Useful LifeAs of December 31, 2014			2014		2013
	Buildings and leasehold improvements	21	years	$	5,780	$	5,239
	Furniture, fixtures and equipment	7	years		2,930		2,383
	Construction in process		N/A		775		828
	Land		N/A		820		799
	Property and equipment, at cost				10,305		9,249
	Less: Accumulated depreciation				2,167		1,599
	Property and equipment, net			$	8,138	$	7,650

Goodwill_Tables

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2014
Schedule of Goodwill	Goodwill
					NBCUniversal
	(in millions)			Cable Communications		Cable Networks		Broadcast Television		Filmed Entertainment		Theme Parks		Corporate and Other		Total
	Balance, December 31, 2012		$	12,206	$	13,026	$	761	$	1	$	982	$	9	$	26,985
	Acquisitions			-		39		3		-		-		-		42
	Adjustments			-		65		5		-		-		1		71
	Balance, December 31, 2013			12,206		13,130		769		1		982		10		27,098
	Acquisitions			11		20		-		15		-		181		227
	Adjustments(a)			-		-202		-2		195		-		-		-9
	Balance, December 31, 2014		$	12,217	$	12,948	$	767	$	211	$	982	$	191	$	27,316
	(a) Adjustments to goodwill in 2014 were primarily related to the reclassification of Fandango, our movie ticketing and entertainment business, from our Cable Networks segment to our Filmed Entertainment segment.
Other Intangible Assets	Intangible Assets
						2014				2013
	December 31 (in millions)		Weighted-Average Original Useful Life as of December 31, 2014			Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
	Indefinite-Lived Intangible Assets:
		Franchise rights		N/A	$	59,364			$	59,364
		Trade names		N/A		3,083				3,089
		FCC licenses		N/A		651				652
	Finite-Lived Intangible Assets:
		Customer relationships	19	years		15,129	$	-5,495		15,037	$	-4,772
		Software	5	years		5,040		-2,832		4,271		-2,405
		Cable franchise renewal costs and contractual operating rights	10	years		1,418		-792		1,360		-745
		Patents and other technology rights	8	years		373		-330		361		-307
		Other agreements and rights	20	years		1,456		-721		1,433		-645
	Total				$	86,514	$	-10,170	$	85,567	$	-8,874
Amortization of Intangible Assets	Estimated Amortization Expense of Finite-Lived Intangible Assets
	(in millions)
	2015	$	1,619
	2016	$	1,457
	2017	$	1,296
	2018	$	1,053
	2019	$	842
NBCUniversal Media, LLC [Member]
Schedule of Goodwill	Goodwill
	(in millions)			Cable Networks		Broadcast Television		Filmed Entertainment		Theme Parks		Total
	Balance, December 31, 2012		$	13,026	$	761	$	1	$	982	$	14,770
	Acquisitions			39		3		-		-		42
	Adjustments			65		5		-		-		70
	Balance, December 31, 2013			13,130		769		1		982		14,882
	Acquisitions			20		-		15		-		35
	Adjustments(a)			-202		-2		195		-		-9
	Balance, December 31, 2014		$	12,948	$	767	$	211	$	982	$	14,908
	(a) Adjustments to goodwill in 2014 were primarily related to the reclassification of Fandango, our movie ticketing and entertainment business, from our Cable Networks segment to our Filmed Entertainment segment.
Other Intangible Assets	Intangible Assets
						2014				2013
	December 31 (in millions)		Weighted-Average Original Useful Life as of December 31, 2014			Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
	Finite-Lived Intangible Assets:
		Customer relationships	19 years		$	13,093	$	-3,636	$	13,086	$	-2,982
		Software	5 years			657		-329		522		-240
		Other	21 years			1,556		-864		1,511		-781
	Indefinite-Lived Intangible Assets:
		Trade names	N/A			3,059				3,089
		FCC licenses	N/A			651				652
	Total				$	19,016	$	-4,829	$	18,860	$	-4,003
Amortization of Intangible Assets	Estimated Amortization Expense of Finite-Lived Intangible Assets
	(in millions)
	2015	$	777
	2016	$	748
	2017	$	747
	2018	$	743
	2019	$	740

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Schedule of Long-Term Debt	Long-Term Debt Outstanding
	December 31 (in millions)	Weighted-Average Interest Rate as of December 31, 2014			2014		2013
	Commercial paper	0.373	%	$	845	$	1,350
	Revolving bank credit facilities	—	%		-		1,250
	Senior notes with maturities of 5 years or less	4.642	%		15,334		15,080
	Senior notes with maturities between 5 and 10 years	4.822	%		10,527		11,533
	Senior notes with maturities greater than 10 years(a)	5.737	%		20,937		18,010
	Other, including capital lease obligations	—			591		624
	Total debt	4.95	%(b)		48,234		47,847
	Less: Current portion				4,217		3,280
	Long-term debt			$	44,017	$	44,567
	(a) The December 31, 2014 and 2013 amounts include £625 million of 5.50% notes due 2029 which translated to $974 million and $1 billion, respectively, using the exchange rates as of these dates.
	(b) Includes the effects of our derivative financial instruments.
Debt Maturities	Debt Maturities
	(in millions)	Weighted-Average Interest Rate as of December 31, 2014
	2015	4.99	%		$	4,217
	2016	4.158	%		$	3,530
	2017	6.973	%		$	2,558
	2018	4.124	%		$	4,117
	2019	3.159	%		$	2,205
	Thereafter	5.425	%		$	31,607
Debt Borrowings	2014 Debt Borrowings
	Year ended December 31, 2014 (in millions)
	Comcast 3.600% senior notes due 2024	$	1,200
	Comcast 3.375% senior notes due 2025		1,000
	Comcast 4.200% senior notes due 2034		1,000
	Comcast 4.750% senior notes due 2044		1,000
	Total	$	4,200
Debt Repayments and Repurchases	2014 Debt Repayments
	Year ended December 31, 2014 (in millions)
	NBCUniversal Enterprise revolving credit facility	$	1,250
	Comcast 5.300% senior notes due 2014		1,000
	NBCUniversal 2.100% senior notes due 2014		900
	Other		25
	Total	$	3,175
NBCUniversal Media, LLC [Member]
Schedule of Long-Term Debt	Long-Term Debt Outstanding
	December 31 (in millions)	Weighted-Average Interest Rate as of December 31, 2014		2014			2013
	Senior notes with maturities of 5 years or less	3.254	%	$	2,005	$	2,917
	Senior notes with maturities between 5 and 10 years	4.389	%		4,996		4,996
	Senior notes with maturities greater than 10 years	5.614	%		3,204		3,205
	Other, including capital lease obligations	—			44		47
	Total debt	4.46	%(a)		10,249		11,165
	Less: Current portion				1,023		906
	Long-term debt			$	9,226	$	10,259
	(a) Includes the effects of our derivative financial instruments.
Debt Maturities	Debt Maturities
	(in millions)	Weighted-Average Interest Rate as of December 31, 2014
	2015	3.633	%		$	1,023
	2016	2.894	%		$	1,008
	2017	6.296	%		$	2
	2018	6.307	%		$	2
	2019	6.329	%		$	2
	Thereafter	4.871	%		$	8,212

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Assets and Liabilities Measured on Recurring Basis	Recurring Fair Value Measures
			Fair Value as of December 31, 2014								Fair Value as of December 31, 2013
	(in millions)		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
	Assets
	Trading securities	$	523	$	-	$	-	$	523	$	3,956	$	-	$	-	$	3,956
	Available-for-sale securities		1		121		10		132		260		118		11		389
	Interest rate swap agreements		-		84		-		84		-		110		-		110
	Other		-		64		7		71		-		80		1		81
	Total	$	524	$	269	$	17	$	810	$	4,216	$	308	$	12	$	4,536
	Liabilities
	Derivative component of prepaid forward sale agreements and indexed debt instruments	$	-	$	361	$	-	$	361	$	-	$	2,816	$	-	$	2,816
	Contractual obligations		-		-		883		883		-		-		747		747
	Contingent consideration		-		-		644		644		-		-		684		684
	Other		-		8		-		8		-		16		-		16
	Total	$	-	$	369	$	1,527	$	1,896	$	-	$	2,832	$	1,431	$	4,263
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	Changes in Contractual Obligations and Contingent Consideration
	(in millions)		Contractual Obligations		Contingent Consideration
	Balance, December 31, 2013	$	747	$	684
	Fair value adjustments		208		31
	Payments		-72		-71
	Balance, December 31, 2014	$	883	$	644
NBCUniversal Media, LLC [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	Changes in Contractual Obligations
	(in millions)
	Balance, December 31, 2013	$	747
	Fair value adjustments		208
	Payments		-72
	Balance, December 31, 2014	$	883

Postretirement_Pension_and_Oth

Postretirement, Pension and Other Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Postretirement And Pension Benefits				2014					2013						2012
	Year ended December 31 (in millions)			Postretirement Benefits		Pension Benefits			Postretirement Benefits			Pension Benefits			Postretirement Benefits			Pension Benefits
	Benefit obligation		$	837		$	581		$	633		$	498		$	703		$	805
	Fair value of plan assets(a)			-			242			-			220			-			403
	Plan funded status and recorded
		benefit obligation		-837			-339			-633			-278			-703			-402
	Portion of benefit obligation not
		yet recognized in benefits expense		46			53			-110			-3			17			151
	Benefits expense(b)			59			14			65			12			60			163
	Discount rate			4.25	%	3.75-4.25		%		5.00-5.25	%	4.50-5.25		%		4.25	%	3.25-4.25		%
	Expected return on plan assets			N/A			5	%		N/A			5	%		N/A			5	%
	(a) The fair value of the plan assets are primarily based on Level 1 inputs that use quoted market prices for identical financial instruments in an active market.
	(b) We did not recognize service costs related to our pension plans in 2014 and 2013 as the plans were frozen. The 2012 amount included service costs related to our pension benefits of $139 million.
Deferred Compensation Plans	Year ended December 31 (in millions)		2014		2013		2012
	Benefit obligation	$	1,774	$	1,434	$	1,247
	Interest expense	$	149	$	128	$	107
Benefit Obligation and Expense for Our Split-Dollar Life Insurance Agreements	Year ended December 31 (in millions)		2014		2013		2012
	Benefit obligation	$	217	$	212	$	202
	Other operating and administrative expenses	$	52	$	50	$	58
NBCUniversal Media, LLC [Member]
Postretirement And Pension Benefits			2014						2013						2012
	Year ended December 31 (in millions)		Postretirement Benefits			Pension Benefits			Postretirement Benefits			Pension Benefits			Postretirement Benefits			Pension Benefits
	Benefit obligation		$	209		$	581		$	158		$	498		$	177		$	546
	Fair value of plan assets(a)			-			242			-			220			-			217
	Plan funded status and recorded
		benefit obligation		-209			-339			-158			-278			-177			-329
	Portion of benefit obligation not yet
		recognized in benefit expense		-3			53			-44			-3			-11			53
	Benefits expense(b)			12			14			14			12			15			142
	Discount rate			4.25	%		3.75-4.25	%		5.25	%		4.50-5.25	%		4.25	%		3.75-4.25	%
	Expected return on plan assets			N/A			5	%		N/A			5	%		N/A			5	%
	(a) The fair value of the plan assets are primarily based on Level 1 inputs that use quoted market prices for identical financial instruments in an active market.
	(b) We did not recognize service costs related to our pension plans in 2014 and 2013 as the plans were frozen. The 2012 amount included service costs related to our pension benefits of $134 million.
Deferred Compensation Plans	Year ended December 31 (in millions)		2014		2013		2012
	Benefit obligation	$	349	$	250	$	163
	Interest expense	$	24	$	18	$	11

Equity_Tables

Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Changes in Common Stock	Shares of Common Stock Outstanding
	(in millions)	A	A Special	B
	Balance, December 31, 2011	2,095	601	9
	Stock compensation plans	24	3	-
	Repurchases and retirements of common stock	-	-96	-
	Employee stock purchase plans	3	-	-
	Balance, December 31, 2012	2,122	508	9
	Stock compensation plans	14	-	-
	Repurchases and retirements of common stock	-	-49	-
	Employee stock purchase plans	2	-	-
	Balance, December 31, 2013	2,138	459	9
	Stock compensation plans	13	-	-
	Repurchases and retirements of common stock	-22	-59	-
	Employee stock purchase plans	2	-	-
	Balance, December 31, 2014	2,131	400	9
Aggregate Share Repurchases	Share Repurchases
	Year ended December 31 (in millions)		2014		2013		2012
	Cash consideration	$	4,251	$	2,000	$	3,000
	Shares repurchased		81		49		96
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Accumulated Other Comprehensive Income (Loss)
	December 31 (in millions)			2014		2013
	Unrealized gains (losses) on marketable securities		$	1	$	67
	Deferred gains (losses) on cash flow hedges			-4		-45
	Unrecognized gains (losses) on employee benefit obligations			-68		71
	Cumulative translation adjustments			-75		-37
	Accumulated other comprehensive income (loss), net of deferred taxes		$	-146	$	56
NBCUniversal Media, LLC [Member]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Accumulated Other Comprehensive Income (Loss)
	December 31 (in millions)		2014		2013
	Deferred gains (losses) on cash flow hedges		$	20	$	-5
	Unrecognized gains (losses) on employee benefit obligations			-61		45
	Cumulative translation adjustments			-118		-56
	Accumulated other comprehensive income (loss)		$	-159	$	-16

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Recognized Share-Based Compensation Expense	Recognized Share-Based Compensation Expense
	Year ended December 31 (in millions)		2014		2013		2012
	Stock options	$	160	$	139	$	131
	Restricted share units		231		175		154
	Employee stock purchase plans		23		20		16
	Total	$	414	$	334	$	301
Stock Option Activity	Stock Options and Restricted Share Units
	As of December 31, 2014, unless otherwise stated (in millions, except per share data)			Stock Options		RSUs
	Awards granted during 2014			16		8
	Weighted-average exercise price of awards granted during 2014		$	50.03
	Stock options outstanding and nonvested RSUs			98		24
	Weighted-average exercise price of stock options outstanding		$	30.29
	Weighted-average fair value at grant date of nonvested RSUs				$	34.11
Stock Option Fair Value and Significant Assumptions	Year ended December 31			2014			2013			2012
	RSUs fair value		$	47.91		$	38.28		$	27.8
	Stock options fair value		$	11.11		$	8.8		$	7.38
	Stock Option Valuation Assumptions:
		Dividend yield		1.8	%		1.9	%		2.2	%
		Expected volatility		24	%		25	%		29	%
		Risk-free interest rate		2.2	%		1.3	%		1.7	%
		Expected option life (in years)		6.5			7			7
NBCUniversal Media, LLC [Member]
Recognized Share-Based Compensation Expense	Recognized Share-Based Compensation Expense
	Year ended December 31 (in millions)	2014		2013		2012
	Stock options	$	16	$	15	$	15
	Restricted share units		69		42		28
	Employee stock purchase plans		6		5		4
	Total	$	91	$	62	$	47
Stock Option Fair Value and Significant Assumptions	Year ended December 31			2014			2013			2012
	RSUs fair value		$	48.04		$	37.79		$	27.51
	Stock options fair value		$	11.09		$	8.86		$	7.42
	Stock Option Valuation Assumptions:
		Dividend yield		1.8	%		1.9	%		2.2	%
		Expected volatility		24	%		25.2	%		29	%
		Risk-free interest rate		2.2	%		1.3	%		1.7	%
		Expected option life (in years)		6.5			7			7

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Components of Income Tax Expense	Components of Income Tax Expense
	Year ended December 31 (in millions)			2014		2013		2012
	Current Expense (Benefit):
		Federal	$	2,392	$	3,183	$	3,004
		State		174		581		432
		Foreign		142		200		169
				2,708		3,964		3,605
	Deferred Expense (Benefit):
		Federal		1,000		-76		160
		State		173		108		-40
		Foreign		-8		-16		19
				1,165		16		139
	Income tax expense		$	3,873	$	3,980	$	3,744
Schedule of Items That Effect Income Tax Expense	Year ended December 31 (in millions)		2014		2013		2012
	Federal tax at statutory rate	$	4,363	$	3,890	$	4,063
	State income taxes, net of federal benefit		329		319		178
	Foreign income taxes, net of federal credit		-		15		92
	Nontaxable income attributable to noncontrolling interests		-62		-103		-620
	Adjustments to uncertain and effectively settled tax positions, net		-408		58		114
	Accrued interest on uncertain and effectively settled tax positions, net		-235		114		23
	Other		-114		-313		-106
	Income tax expense	$	3,873	$	3,980	$	3,744
Components of Net Deferred Tax Liability	Components of Net Deferred Tax Liability
	December 31 (in millions)				2014		2013
	Deferred Tax Assets:
		Net operating loss carryforwards		$	448	$	495
		Differences between book and tax basis of long-term debt			116		117
		Nondeductible accruals and other			3,383		3,588
		Less: Valuation allowance			375		405
					3,572		3,795
	Deferred Tax Liabilities:
		Differences between book and tax basis of property and equipment and intangible assets			35,112		34,044
		Differences between book and tax basis of investments			186		473
		Differences between book and tax basis of indexed debt securities			534		610
		Differences between book and tax basis of foreign
			subsidiaries and undistributed foreign earnings		504		367
					36,336		35,494
	Net deferred tax liability			$	32,764	$	31,699
Reconciliation of Unrecognized Tax Benefits	Reconciliation of Unrecognized Tax Benefits
	(in millions)		2014		2013		2012
	Balance, January 1	$	1,701	$	1,573	$	1,435
	Additions based on tax positions related to the current year		63		90		154
	Additions based on tax positions related to prior years		111		201		79
	Additions from acquired subsidiaries		-		268		-
	Reductions for tax positions of prior years		-220		-141		-60
	Reductions due to expiration of statutes of limitations		-448		-3		-3
	Settlements with taxing authorities		-36		-287		-32
	Balance, December 31	$	1,171	$	1,701	$	1,573
NBCUniversal Media, LLC [Member]
Components of Income Tax Expense	Components of Income Tax Expense
	Year ended December 31 (in millions)		2014		2013		2012
	Foreign
		Current income tax expense	$	33	$	77	$	69
		Deferred income tax expense		-8		-16		16
		Withholding tax expense		108		123		103
	U.S. domestic tax expense			10		22		9
	Income tax expense		$	143	$	206	$	197

Supplemental_Financial_Informa1

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014
Receivables	Receivables
	December 31 (in millions)		2014		2013
	Receivables, gross	$	6,885	$	6,972
	Less: Allowance for returns and customer incentives		359		375
	Less: Allowance for doubtful accounts		205		221
	Receivables, net	$	6,321	$	6,376
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)
	December 31 (in millions)			2014		2013
	Unrealized gains (losses) on marketable securities		$	1	$	67
	Deferred gains (losses) on cash flow hedges			-4		-45
	Unrecognized gains (losses) on employee benefit obligations			-68		71
	Cumulative translation adjustments			-75		-37
	Accumulated other comprehensive income (loss), net of deferred taxes		$	-146	$	56
Cash Payments For Interest and Income Taxes	Cash Payments for Interest and Income Taxes
	Year ended December 31 (in millions)		2014		2013		2012
	Interest	$	2,389	$	2,355	$	2,314
	Income taxes	$	3,668	$	3,946	$	2,841
NBCUniversal Media, LLC [Member]
Receivables	Receivables
	December 31 (in millions)		2014		2013
	Receivables, gross	$	5,258	$	5,348
	Less: Allowance for returns and customer incentives		356		372
	Less: Allowance for doubtful accounts		60		65
	Receivables, net	$	4,842	$	4,911
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)
	December 31 (in millions)		2014		2013
	Deferred gains (losses) on cash flow hedges		$	20	$	-5
	Unrecognized gains (losses) on employee benefit obligations			-61		45
	Cumulative translation adjustments			-118		-56
	Accumulated other comprehensive income (loss)		$	-159	$	-16
Cash Payments For Interest and Income Taxes	Cash Payments for Interest and Income Taxes
	Year ended December 31 (in millions)	2014		2013			2012
	Interest	$	485	$	462	$	461
	Income taxes	$	174	$	205	$	169

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments Disclosure [Table Text Block]	As of December 31, 2014 (in millions)		Programming and Talent Commitments		Operating Leases
	2015	$	4,915	$	399
	2016	$	4,657	$	359
	2017	$	3,177	$	299
	2018	$	3,999	$	253
	2019	$	2,793	$	197
	Thereafter	$	26,130	$	754
Rental Expense [Table Text Block]	The table below presents our rent expense charged to operations.
	Year ended December 31 (in millions)		2014		2013		2012
	Rent expense	$	580	$	616	$	688
NBCUniversal Media, LLC [Member]
Commitments Disclosure [Table Text Block]	As of December 31, 2014 (in millions)		Programming and Talent Commitments		Operating Leases
	2015	$	4,898	$	150
	2016	$	4,648	$	135
	2017	$	3,173	$	107
	2018	$	3,998	$	89
	2019	$	2,793	$	73
	Thereafter	$	26,130	$	402
Rental Expense [Table Text Block]	The table below presents our rent expense charged to operations.
	Year ended December 31 (in millions)	2014		2013		2012
	Rent expense	$	222	$	250	$	317

Financial_Data_by_Business_Seg1

Financial Data by Business Segment (Tables)	12 Months Ended
	Dec. 31, 2014
Financial Data by Business Segment	(in millions)			Revenue(f)		Operating Income (Loss) Before Depreciation and Amortization(g)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2014
	Cable Communications(a)		$	44,140	$	18,112	$	6,422	$	11,690	$	6,154	$	140,616
	NBCUniversal
		Cable Networks(b)(c)		9,563		3,589		748		2,841		49		28,582
		Broadcast Television(c)		8,542		734		127		607		76		6,806
		Filmed Entertainment(b)		5,008		711		21		690		11		4,185
		Theme Parks		2,623		1,168		273		895		671		7,017
		Headquarters and Other(d)		13		-613		326		-939		414		6,479
		Eliminations(e)		-321		-1		-		-1		-		-452
	NBCUniversal			25,428		5,588		1,495		4,093		1,221		52,617
	Corporate and Other			709		-778		102		-880		45		5,338
	Eliminations(e)			-1,502		1		-		1		-		-39,232
	Comcast Consolidated		$	68,775	$	22,923	$	8,019	$	14,904	$	7,420	$	159,339
	(in millions)			Revenue(f)		Operating Income (Loss) Before Depreciation and Amortization(g)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2013
	Cable Communications(a)		$	41,836	$	17,205	$	6,394	$	10,811	$	5,403	$	132,082
	NBCUniversal
		Cable Networks(b)		9,201		3,501		734		2,767		67		29,413
		Broadcast Television		7,120		345		98		247		65		6,723
		Filmed Entertainment(b)		5,452		483		15		468		9		3,549
		Theme Parks		2,235		1,004		300		704		580		6,608
		Headquarters and Other(d)		31		-588		264		-852		439		6,002
		Eliminations(e)		-389		-13		-		-13		-		-556
	NBCUniversal			23,650		4,732		1,411		3,321		1,160		51,739
	Corporate and Other			600		-489		66		-555		33		8,152
	Eliminations(e)			-1,429		-14		-		-14		-		-33,160
	Comcast Consolidated		$	64,657	$	21,434	$	7,871	$	13,563	$	6,596	$	158,813
	(in millions)			Revenue(f)		Operating Income (Loss) Before Depreciation and Amortization(g)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures
	2012
	Cable Communications(a)		$	39,604	$	16,255	$	6,405	$	9,850	$	4,921
	NBCUniversal
		Cable Networks(b)		8,727		3,303		735		2,568		150
		Broadcast Television(c)		8,200		358		97		261		65
		Filmed Entertainment(b)		5,159		79		16		63		7
		Theme Parks		2,085		953		268		685		272
		Headquarters and Other(d)		43		-603		210		-813		269
		Eliminations(e)		-402		17		-		17		-
	NBCUniversal			23,812		4,107		1,326		2,781		763
	Corporate and Other			498		-376		67		-443		30
	Eliminations(e)			-1,344		-9		-		-9		-
	Comcast Consolidated		$	62,570	$	19,977	$	7,798	$	12,179	$	5,714
Cable Communications Segment Revenue Sources			2014		2013		2012
	Residential:
		Video	47.1	%	49.1	%	50.4	%
		High-speed Internet	25.6	%	24.7	%	24.1	%
		Voice	8.3	%	8.7	%	9	%
	Business services		9	%	7.7	%	6.5	%
	Advertising		5.5	%	5.2	%	5.8	%
	Other		4.5	%	4.6	%	4.2	%
	Total		100	%	100	%	100	%
NBCUniversal Media, LLC [Member]
Financial Data by Business Segment	(in millions)			Revenue(e)(g)		Operating Income (Loss) Before Depreciation and Amortization(f)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2014
		Cable Networks(a)(b)	$	9,563	$	3,589	$	748	$	2,841	$	49	$	28,582
		Broadcast Television(b)		8,542		734		127		607		76		6,806
		Filmed Entertainment(a)		5,008		711		21		690		11		4,185
		Theme Parks		2,623		1,168		273		895		671		7,017
		Headquarters and Other(c)		13		-613		326		-939		414		6,479
		Eliminations(d)		-321		-1		-		-1		-		-452
	Total		$	25,428	$	5,588	$	1,495	$	4,093	$	1,221	$	52,617
	(in millions)			Revenue(e)(g)		Operating Income (Loss) Before Depreciation and Amortization(f)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures		Assets
	2013
		Cable Networks(a)	$	9,201	$	3,501	$	734	$	2,767	$	67	$	29,413
		Broadcast Television		7,120		345		98		247		65		6,723
		Filmed Entertainment(a)		5,452		483		15		468		9		3,549
		Theme Parks		2,235		1,004		300		704		580		6,608
		Headquarters and Other(c)		31		-588		264		-852		439		6,002
		Eliminations(d)		-389		-13		-		-13		-		-556
	Total		$	23,650	$	4,732	$	1,411	$	3,321	$	1,160	$	51,739
	(in millions)			Revenue(e)(g)		Operating Income (Loss) Before Depreciation and Amortization(f)		Depreciation and Amortization		Operating Income (Loss)		Capital Expenditures
	2012
		Cable Networks(a)	$	8,727	$	3,303	$	735	$	2,568	$	150
		Broadcast Television(b)		8,200		358		97		261		65
		Filmed Entertainment(a)		5,159		79		16		63		7
		Theme Parks		2,085		953		268		685		272
		Headquarters and Other(c)		43		-603		210		-813		269
		Eliminations(d)		-402		17		-		17		-
	Total		$	23,812	$	4,107	$	1,326	$	2,781	$	763
Revenue From External Customers By Geographic Areas Table Text Block		Year ended December 31 (in millions)		2014		2013		2012
		Revenue:
		United States	$	20,995	$	18,887	$	19,348
		Foreign	$	4,433	$	4,763	$	4,464

Quarterly_Financial_Informatio1

Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information
Quarterly Financial Information (Unaudited)	(in millions, except per share data)		First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
	2014
	Revenue	$	17,408	$	16,844	$	16,791	$	17,732	$	68,775
	Operating income	$	3,568	$	3,804	$	3,745	$	3,787	$	14,904
	Net income attributable to Comcast Corporation(a)	$	1,871	$	1,992	$	2,592	$	1,925	$	8,380
	Basic earnings per common share attributable to Comcast Corporation shareholders	$	0.72	$	0.77	$	1	$	0.75	$	3.24
	Diluted earnings per common share attributable to Comcast Corporation shareholders	$	0.71	$	0.76	$	0.99	$	0.74	$	3.2
	Dividends declared per common share	$	0.225	$	0.225	$	0.225	$	0.225	$	0.9
	2013
	Revenue	$	15,310	$	16,270	$	16,151	$	16,926	$	64,657
	Operating income	$	3,067	$	3,435	$	3,414	$	3,647	$	13,563
	Net income attributable to Comcast Corporation	$	1,437	$	1,734	$	1,732	$	1,913	$	6,816
	Basic earnings per common share attributable to Comcast Corporation shareholders	$	0.55	$	0.66	$	0.66	$	0.73	$	2.6
	Diluted earnings per common share attributable to Comcast Corporation shareholders	$	0.54	$	0.65	$	0.65	$	0.72	$	2.56
	Dividends declared per common share	$	0.195	$	0.195	$	0.195	$	0.195	$	0.78
	(a) In the third quarter of 2014, net income attributable to Comcast Corporation included $724 million of favorable income tax adjustments resulting from a reduction in our accruals for uncertain tax positions and the related accrued interest on these tax positions. See Note 15 for additional information.

Condensed_Consolidating_Financ1

Condensed Consolidating Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014
Condensed Consolidating Financial Information [Abstract]
Condensed Consolidating Financial Statements	Condensed Consolidating Balance Sheet
	December 31, 2014 (in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Assets
		Cash and cash equivalents	$	-	$	-	$	-	$	-	$	385	$	3,525	$	-	$	3,910
		Investments		-		-		-		-		-		602		-		602
		Receivables, net		-		-		-		-		-		6,321		-		6,321
		Programming rights		-		-		-		-		-		839		-		839
		Other current assets		267		-		-		-		41		1,551		-		1,859
	Total current assets			267		-		-		-		426		12,838		-		13,531
	Film and television costs			-		-		-		-		-		5,727		-		5,727
	Investments			36		-		-		-		378		2,721		-		3,135
	Investments in and amounts due from subsidiaries eliminated upon consolidation			84,142		103,420		110,323		58,677		41,239		98,152		-495,953		-
	Property and equipment, net			199		-		-		-		-		30,754		-		30,953
	Franchise rights			-		-		-		-		-		59,364		-		59,364
	Goodwill			-		-		-		-		-		27,316		-		27,316
	Other intangible assets, net			11		-		-		-		-		16,969		-		16,980
	Other noncurrent assets, net			1,224		148		-		-		92		1,949		-1,080		2,333
	Total assets		$	85,879	$	103,568	$	110,323	$	58,677	$	42,135	$	255,790	$	-497,033	$	159,339
	Liabilities and Equity
		Accounts payable and accrued expenses related to trade creditors	$	19	$	-	$	-	$	1	$	-	$	5,618	$	-	$	5,638
		Accrued participations and residuals		-		-		-		-		-		1,347		-		1,347
		Accrued expenses and other current liabilities		1,547		283		233		47		331		3,767		-		6,208
		Current portion of long-term debt		1,650		-		-		677		1,006		884		-		4,217
	Total current liabilities			3,216		283		233		725		1,337		11,616		-		17,410
	Long-term debt, less current portion			27,616		126		1,827		822		9,218		4,408		-		44,017
	Deferred income taxes			-		701		-		-		67		33,127		-936		32,959
	Other noncurrent liabilities			2,336		-		-		-		1,143		7,484		-144		10,819
	Redeemable noncontrolling interests
		and redeemable subsidiary preferred stock		-		-		-		-		-		1,066		-		1,066
	Equity:
		Common stock		30		-		-		-		-		-		-		30
		Other shareholders’ equity		52,681		102,458		108,263		57,130		30,370		197,732		-495,953		52,681
	Total Comcast Corporation shareholders’ equity			52,711		102,458		108,263		57,130		30,370		197,732		-495,953		52,711
	Noncontrolling interests			-		-		-		-		-		357		-		357
	Total equity			52,711		102,458		108,263		57,130		30,370		198,089		-495,953		53,068
	Total liabilities and equity		$	85,879	$	103,568	$	110,323	$	58,677	$	42,135	$	255,790	$	-497,033	$	159,339
	Condensed Consolidating Balance Sheet
	December 31, 2013(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Assets
		Cash and cash equivalents	$	-	$	-	$	-	$	-	$	336	$	1,382	$	-	$	1,718
		Investments		-		-		-		-		-		3,573		-		3,573
		Receivables, net		-		-		-		-		-		6,376		-		6,376
		Programming rights		-		-		-		-		-		928		-		928
		Other current assets		237		-		-		-		35		1,208		-		1,480
	Total current assets			237		-		-		-		371		13,467		-		14,075
	Film and television costs			-		-		-		-		-		4,994		-		4,994
	Investments			11		-		-		-		374		3,385		-		3,770
	Investments in and amounts due from subsidiaries eliminated upon consolidation			79,956		97,429		102,673		54,724		40,644		85,164		-460,590		-
	Property and equipment, net			220		-		-		-		-		29,620		-		29,840
	Franchise rights			-		-		-		-		-		59,364		-		59,364
	Goodwill			-		-		-		-		-		27,098		-		27,098
	Other intangible assets, net			11		-		-		-		-		17,318		-		17,329
	Other noncurrent assets, net			1,078		145		-		-		103		1,899		-882		2,343
	Total assets		$	81,513	$	97,574	$	102,673	$	54,724	$	41,492	$	242,309	$	-461,472	$	158,813
	Liabilities and Equity
		Accounts payable and accrued expenses related to trade creditors	$	8	$	-	$	-	$	-	$	-	$	5,520	$	-	$	5,528
		Accrued participations and residuals		-		-		-		-		-		1,239		-		1,239
		Accrued expenses and other current liabilities		1,371		266		180		47		323		6,678		-		8,865
		Current portion of long-term debt		2,351		-		-		-		903		26		-		3,280
	Total current liabilities			3,730		266		180		47		1,226		13,463		-		18,912
	Long-term debt, less current portion			25,170		132		1,827		1,505		10,236		5,697		-		44,567
	Deferred income taxes			-		777		-		-		59		31,840		-741		31,935
	Other noncurrent liabilities			1,919		-		-		-		931		8,675		-141		11,384
	Redeemable noncontrolling interests
	and redeemable subsidiary preferred stock		-		-		-		-		-		957		-		957
Equity:
	Common stock		30		-		-		-		-		-		-		30
	Other shareholders’ equity		50,664		96,399		100,666		53,172		29,040		181,313		-460,590		50,664
Total Comcast Corporation shareholders’ equity			50,694		96,399		100,666		53,172		29,040		181,313		-460,590		50,694
Noncontrolling interests			-		-		-		-		-		364		-		364
Total equity			50,694		96,399		100,666		53,172		29,040		181,677		-460,590		51,058
Total liabilities and equity		$	81,513	$	97,574	$	102,673	$	54,724	$	41,492	$	242,309	$	-461,472	$	158,813
Condensed Consolidating Statement of Income
For the Year Ended December 31, 2014(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
Revenue:
	Service revenue	$	-	$	-	$	-	$	-	$	-	$	68,775	$	-	$	68,775
	Management fee revenue		947		-		921		582		-		-		-2,450		-
			947		-		921		582		-		68,775		-2,450		68,775
Costs and Expenses:
	Programming and production		-		-		-		-		-		20,912		-		20,912
	Other operating and administrative		751		-		921		582		908		19,150		-2,450		19,862
	Advertising, marketing and promotion		-		-		-		-		-		5,078		-		5,078
	Depreciation		34		-		-		-		-		6,303		-		6,337
	Amortization		6		-		-		-		-		1,676		-		1,682
			791		-		921		582		908		53,119		-2,450		53,871
Operating income (loss)			156		-		-		-		-908		15,656		-		14,904
Other Income (Expense):
	Interest expense		-1,621		-11		-176		-118		-479		-212		-		-2,617
	Investment income (loss), net		3		12		-		-		-7		288		-		296
	Equity in net income (losses) of
	investees, net		9,330		8,843		8,273		6,333		4,523		3,212		-40,417		97
	Other income (expense), net		-		-		-		-		-4		-211		-		-215
			7,712		8,844		8,097		6,215		4,033		3,077		-40,417		-2,439
Income (loss) before income taxes			7,868		8,844		8,097		6,215		3,125		18,733		-40,417		12,465
Income tax (expense) benefit			512		-		62		41		-10		-4,478		-		-3,873
Net income (loss)			8,380		8,844		8,159		6,256		3,115		14,255		-40,417		8,592
Net (income) loss attributable to
	noncontrolling interests and redeemable subsidiary preferred stock		-		-		-		-		-		-212		-		-212
Net income (loss) attributable to
	Comcast Corporation	$	8,380	$	8,844	$	8,159	$	6,256	$	3,115	$	14,043	$	-40,417	$	8,380
Comprehensive income (loss)
	attributable to Comcast Corporation	$	8,178	$	8,807	$	8,162	$	6,257	$	2,972	$	13,980	$	-40,178	$	8,178
Condensed Consolidating Statement of Income
For the Year Ended December 31, 2013(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
Revenue:
	Service revenue	$	-	$	-	$	-	$	-	$	-	$	64,657	$	-	$	64,657
	Management fee revenue		897		-		874		548		-		-		-2,319		-
			897		-		874		548		-		64,657		-2,319		64,657
Costs and Expenses:
	Programming and production		-		-		-		-		-		19,670		-		19,670
	Other operating and administrative		403		-		874		548		855		18,223		-2,319		18,584
	Advertising, marketing and promotion		-		-		-		-		-		4,969		-		4,969
	Depreciation		30		-		-		-		-		6,224		-		6,254
	Amortization		5		-		-		-		-		1,612		-		1,617
			438		-		874		548		855		50,698		-2,319		51,094
Operating income (loss)			459		-		-		-		-855		13,959		-		13,563
Other Income (Expense):
	Interest expense		-1,523		-11		-212		-126		-488		-214		-		-2,574
	Investment income (loss), net		-		-13		-		-		3		586		-		576
	Equity in net income (losses) of
	investees, net		7,509		7,540		7,430		5,473		3,331		1,882		-33,251		-86
	Other income (expense), net		-2		-		2		-		-1		-363		-		-364
			5,984		7,516		7,220		5,347		2,845		1,891		-33,251		-2,448
Income (loss) before income taxes			6,443		7,516		7,220		5,347		1,990		15,850		-33,251		11,115
Income tax (expense) benefit			373		9		73		44		-22		-4,457		-		-3,980
Net income (loss)			6,816		7,525		7,293		5,391		1,968		11,393		-33,251		7,135
Net (income) loss attributable to
	noncontrolling interests and redeemable subsidiary preferred stock		-		-		-		-		-		-319		-		-319
Net income (loss) attributable
	to Comcast Corporation	$	6,816	$	7,525	$	7,293	$	5,391	$	1,968	$	11,074	$	-33,251	$	6,816
Comprehensive income (loss)
	attributable to Comcast Corporation	$	6,883	$	7,521	$	7,276	$	5,392	$	2,017	$	10,969	$	-33,175	$	6,883
Condensed Consolidating Statement of Income
For the Year Ended December 31, 2012(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
Revenue:
	Service revenue	$	-	$	-	$	-	$	-	$	-	$	62,570	$	-	$	62,570
	Management fee revenue		848		-		827		516		-		-		-2,191		-
			848		-		827		516		-		62,570		-2,191		62,570
Costs and Expenses:
	Programming and production		-		-		-		-		-		19,929		-		19,929
	Other operating and administrative		401		-		827		516		899		17,381		-2,191		17,833
	Advertising, marketing and promotion		-		-		-		-		-		4,831		-		4,831
	Depreciation		30		-		-		-		-		6,120		-		6,150
	Amortization		4		-		-		-		-		1,644		-		1,648
			435		-		827		516		899		49,905		-2,191		50,391
Operating income (loss)			413		-		-		-		-899		12,665		-		12,179
Other Income (Expense):
	Interest expense		-1,430		-23		-329		-135		-430		-174		-		-2,521
	Investment income (loss), net		8		3		-		-		5		203		-		219
	Equity in net income (losses) of
	investees, net		6,858		6,536		6,665		4,909		4,402		4,014		-32,425		959
	Other income (expense), net		2		-		-		-		-14		785		-		773
			5,438		6,516		6,336		4,774		3,963		4,828		-32,425		-570
Income (loss) before income taxes			5,851		6,516		6,336		4,774		3,064		17,493		-32,425		11,609
Income tax (expense) benefit			352		7		115		47		-9		-4,256		-		-3,744
Net income (loss)			6,203		6,523		6,451		4,821		3,055		13,237		-32,425		7,865
Net (income) loss attributable to
	noncontrolling interests and redeemable subsidiary preferred stock		-		-		-		-		-		-1,662		-		-1,662
Net income (loss) attributable to
	Comcast Corporation	$	6,203	$	6,523	$	6,451	$	4,821	$	3,055	$	11,575	$	-32,425	$	6,203
Comprehensive income (loss)
	attributable to Comcast Corporation	$	6,370	$	6,523	$	6,460	$	4,821	$	3,068	$	11,703	$	-32,575	$	6,370
Condensed Consolidating Statement of Cash Flows
For the Year Ended December 31, 2014(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Net cash provided by (used in) operating activities	$	-354	$	9	$	-57	$	-82	$	-1,299	$	18,728	$	-	$	16,945
Investing Activities:
	Net transactions with affiliates		4,784		-9		57		82		2,247		-7,161		-		-
	Capital expenditures		-3		-		-		-		-		-7,417		-		-7,420
	Cash paid for intangible assets		-6		-		-		-		-		-1,116		-		-1,122
	Acquisitions and construction of real estate properties		-		-		-		-		-		-43		-		-43
	Acquisitions, net of cash acquired		-		-		-		-		-		-477		-		-477
	Proceeds from sales of businesses and investments		-		-		-		-		8		658		-		666
	Return of capital from investees		-		-		-		-		1		24		-		25
	Purchases of investments		-19		-		-		-		-10		-162		-		-191
	Other		-		-		-		-		4		-175		-		-171
	Net cash provided by (used in) investing activities		4,756		-9		57		82		2,250		-15,869		-		-8,733
Financing Activities:
	Proceeds from (repayments of) short-term borrowings, net		-1,350		-		-		-		-		846		-		-504
	Proceeds from borrowings		4,180		-		-		-		-		2		-		4,182
	Repurchases and repayments of debt		-1,000		-		-		-		-902		-1,273		-		-3,175
	Repurchases and retirements of common stock		-4,251		-		-		-		-		-		-		-4,251
	Dividends paid		-2,254		-		-		-		-		-		-		-2,254
	Issuances of common stock		35		-		-		-		-		-		-		35
	Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock		-		-		-		-		-		-220		-		-220
	Other		238		-		-		-		-		-71		-		167
	Net cash provided by (used in) financing activities		-4,402		-		-		-		-902		-716		-		-6,020
Increase (decrease) in cash and cash equivalents			-		-		-		-		49		2,143		-		2,192
Cash and cash equivalents, beginning of year			-		-		-		-		336		1,382		-		1,718
Cash and cash equivalents, end of year		$	-	$	-	$	-	$	-	$	385	$	3,525	$	-	$	3,910
Condensed Consolidating Statement of Cash Flows
For the Year Ended December 31, 2013(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Net cash provided by (used in) operating activities	$	-600	$	-3	$	-151	$	-94	$	-1,102	$	16,110	$	-	$	14,160
Investing Activities:
	Net transactions with affiliates		66		3		2,248		332		-470		-2,179		-		-
	Capital expenditures		-7		-		-		-		-		-6,589		-		-6,596
	Cash paid for intangible assets		-4		-		-		-		-		-1,005		-		-1,009
	Acquisitions and construction of real estate properties		-		-		-		-		-		-1,904		-		-1,904
	Acquisitions, net of cash acquired		-		-		-		-		-		-99		-		-99
	Proceeds from sales of businesses and investments		-		-		-		-		2		1,081		-		1,083
	Return of capital from investees		-		-		-		-		128		21		-		149
	Purchases of investments		-11		-		-		-		-3		-1,209		-		-1,223
	Other		-		-		-		-		-20		105		-		85
	Net cash provided by (used in) investing activities		44		3		2,248		332		-363		-11,778		-		-9,514
Financing Activities:
	Proceeds from (repayments of) short-term borrowings, net		1,349		-		-		-		-		-4		-		1,345
	Proceeds from borrowings		2,933		-		-		-		-		-		-		2,933
	Repurchases and repayments of debt		-		-		-2,097		-238		-88		-21		-		-2,444
	Repurchases and retirements of common stock		-2,000		-		-		-		-		-		-		-2,000
	Dividends paid		-1,964		-		-		-		-		-		-		-1,964
	Issuances of common stock		40		-		-		-		-		-		-		40
	Purchase of NBCUniversal noncontrolling common equity interest		-		-		-		-		-3,200		-7,561		-		-10,761
	Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock		-		-		-		-		-		-215		-		-215
	Settlement of Station Venture liability		-		-		-		-		-		-602		-		-602
	Other		198		-		-		-		-40		-369		-		-211
	Net cash provided by (used in) financing activities		556		-		-2,097		-238		-3,328		-8,772		-		-13,879
Increase (decrease) in cash and cash equivalents			-		-		-		-		-4,793		-4,440		-		-9,233
Cash and cash equivalents, beginning of year			-		-		-		-		5,129		5,822		-		10,951
Cash and cash equivalents, end of year		$	-	$	-	$	-	$	-	$	336	$	1,382	$	-	$	1,718
Condensed Consolidating Statement of Cash Flows
For the Year Ended December 31, 2012(in millions)			Comcast Parent		Comcast Holdings		CCCL Parent		Combined CCHMO Parents		NBCUniversal Media Parent		Non-Guarantor Subsidiaries		Elimination and Consolidation Adjustments		Consolidated Comcast Corporation
	Net cash provided by (used in) operating activities	$	-362	$	-7	$	-177	$	-114	$	-1,347	$	16,861	$	-	$	14,854
Investing Activities:
	Net transactions with affiliates		3,845		206		177		667		4,850		-9,745		-		-
	Capital expenditures		-10		-		-		-		-		-5,704		-		-5,714
	Cash paid for intangible assets		-6		-		-		-		-		-917		-		-923
	Acquisitions, net of cash acquired		-		-		-		-		-		-90		-		-90
	Proceeds from sales of businesses and investments		-		-		-		-		-		3,102		-		3,102
	Return of capital from investees		-		-		-		-		-		2,362		-		2,362
	Purchases of investments		-		-		-		-		-19		-278		-		-297
	Other		-		3		-		-		-22		93		-		74
	Net cash provided by (used in) investing activities		3,829		209		177		667		4,809		-11,177		-		-1,486
Financing Activities:
	Proceeds from (repayments of) short-term borrowings, net		-1		-		-		-		-550		7		-		-544
	Proceeds from borrowings		2,536		-		-		-		1,995		13		-		4,544
	Repurchases and repayments of debt		-1,726		-202		-		-553		-2		-398		-		-2,881
	Repurchases and retirements of common stock		-3,000		-		-		-		-		-		-		-3,000
	Dividends paid		-1,608		-		-		-		-		-		-		-1,608
	Issuances of common stock		233		-		-		-		-		-		-		233
	Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock		-		-		-		-		-		-691		-		-691
	Other		99		-		-		-		-14		-175		-		-90
	Net cash provided by (used in) financing activities		-3,467		-202		-		-553		1,429		-1,244		-		-4,037
Increase (decrease) in cash and cash equivalents			-		-		-		-		4,891		4,440		-		9,331
Cash and cash equivalents, beginning of year			-		-		-		-		238		1,382		-		1,620
Cash and cash equivalents, end of year		$	-	$	-	$	-	$	-	$	5,129	$	5,822	$	-	$	10,951

Schedule_II_Valuation_and_Qual1

Schedule II Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2014
Schedule II-Valuation and Qualifying Accounts	Comcast Corporation and Subsidiaries
	Schedule II — Valuation and Qualifying Accounts
	Year ended December 31, 2014, 2013 and 2012
	Year Ended December 31 (in millions)			Balance at Beginning of Year		Additions Charged to Costs and Expenses(a)		Deductions from Reserves(a)		Balance at End of Year
	2014
		Allowance for doubtful accounts	$	221	$	162	$	178	$	205
		Allowance for returns and customer incentives		375		932		948		359
		Valuation allowance on deferred tax assets		405		33		63		375
	2013
		Allowance for doubtful accounts	$	198	$	317	$	294	$	221
		Allowance for returns and customer incentives		307		811		743		375
		Valuation allowance on deferred tax assets		355		71		21		405
	2012
		Allowance for doubtful accounts	$	202	$	293	$	297	$	198
		Allowance for returns and customer incentives		425		663		781		307
		Valuation allowance on deferred tax assets		297		61		3		355
	(a) Additions and deductions related to allowance for returns and customer incentives include amounts for distribution on behalf of third parties. Additions and deductions related to allowance for returns and customer incentives for the years ended December 31, 2013 and 2012 also reflect corrections to change amounts that were previously recorded net.
NBCUniversal Media, LLC [Member]
Schedule II-Valuation and Qualifying Accounts	NBCUniversal Media, LLC
	Schedule II — Valuation and Qualifying Accounts
	Year ended December 31, 2014, 2013 and 2012
	Year Ended December 31 (in millions)			Balance at Beginning of Year		Additions Charged to Costs and Expenses(a)		Deductions from Reserves(a)		Balance at End of Year
	2014
		Allowance for doubtful accounts	$	65	$	11	$	16	$	60
		Allowance for returns and customer incentives		372		930		946		356
		Valuation allowance on deferred tax assets		60		33		6		87
	2013
		Allowance for doubtful accounts	$	46	$	33	$	14	$	65
		Allowance for returns and customer incentives		307		808		743		372
		Valuation allowance on deferred tax assets		73		8		21		60
	2012
		Allowance for doubtful accounts	$	34	$	19	$	7	$	46
		Allowance for returns and customer incentives		425		663		781		307
		Valuation allowance on deferred tax assets		53		23		3		73
	(a) Additions and deductions related to allowance for returns and customer incentives include amounts for distribution on behalf of third parties. Additions and deductions related to allowance for returns and customer incentives for the years ended December 31, 2013 and 2012 also reflect corrections to change amounts that were previously recorded net.

Business_and_Basis_of_Presenta1

Business and Basis of Presentation (Details)	Dec. 31, 2014	Mar. 19, 2013
	numberofcustomers
Remaining equity interest acquired		49.00%
Total customer relationships	27,000,000
NBCUniversal Media, LLC [Member]
Remaining equity interest acquired		49.00%
Video Customers [Member]
Number of customers	22,400,000
High-speed Internet Customers [Member]
Number of customers	22,000,000
Voice Customers [Member]
Number of customers	11,200,000

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share
Net income attributable to Parent	$1,925	$2,592	$1,992	$1,871	$1,913	$1,732	$1,734	$1,437	$8,380	$6,816	$6,203
Basic shares attributable to Comcast Corporation shareholders									2,583	2,625	2,678
Assumed exercise or issuance of shares relating to stock plans									37	40	39
Diluted shares attributable to Comcast Corporation shareholders									2,620	2,665	2,717
Basic earnings per common share attributable to Comcast Corporation shareholders	$0.75	$1	$0.77	$0.72	$0.73	$0.66	$0.66	$0.55	$3.24	$2.60	$2.32
Diluted earnings per common share attributable to Comcast Corporation shareholders	$0.74	$0.99	$0.76	$0.71	$0.72	$0.65	$0.65	$0.54	$3.20	$2.56	$2.28

Significant_Transactions_Narra

Significant Transactions (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Mar. 19, 2013
Significant Transactions [Line Items]
Purchase of NBCUniversal noncontrolling interest	$16,700,000,000
Consideration transferred related to the Redemption Transaction and purchase of certain properties	725,000,000
Remaining equity interest acquired			49.00%
Company Shares Exchanged For Each Acquiree Share		2.875
NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Purchase of NBCUniversal noncontrolling interest	16,700,000,000
Consideration transferred related to the Redemption Transaction and purchase of certain properties	725,000,000
Remaining equity interest acquired			49.00%
Redemption percentage	15.00%
Comcast Corporation [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Ownership percentage in NBCUniversal Holdings	96.00%
Comcast Cash On Hand
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	11,400,000,000
Comcast Cash On Hand | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	11,400,000,000
NBCUniversal Cash On Hand [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Portion Of Consideration Transferred Funded By NBCUniversal	4,600,000,000
NBCUniversal Enterprise Senior Unsecured Debt Securities [Member]
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	4,000,000,000
NBCUniversal Enterprise Senior Unsecured Debt Securities [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	4,000,000,000
Commercial Paper Program
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	750,000,000
Commercial Paper Program | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	750,000,000
Nbcuniversal Holdings Preferred Stock [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Preferred stock dividend rate percentage	8.25%
Preferred stock liquidition preference value	9,400,000,000
Preferred stock dividend reset rate percentage description	On March 1, 2018, and thereafter on every fifth anniversary of such date, this rate will reset to 7.44% plus the yield on actively traded United States Treasury securities having a 5 year maturity.
Thirty Rockefeller Plaza And Englewood Cliffs [Member]
Significant Transactions [Line Items]
Payments related to acquisition of real estate properties	1,400,000,000
Thirty Rockefeller Plaza And Englewood Cliffs [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Payments related to acquisition of real estate properties	1,400,000,000
NBCUniversal Enterprise [Member]
Significant Transactions [Line Items]
Preferred stock dividend rate percentage	5.25%
Fair value of redeemable preferred stock	741,000,000	751,000,000
NBCUniversal Enterprise [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Ownership percentage in NBCUniversal Holdings	4.00%
Merger Agreement Undertaking Number Of Divested Customers [Member]
Significant Transactions [Line Items]
Number of customers		3,000,000
Comcast Corporate Shareholders [Member]
Significant Transactions [Line Items]
Ownership Percentage In SpinCo		67.00%
New Charter [Member]
Significant Transactions [Line Items]
Ownership Percentage In SpinCo		33.00%
Transaction-Related Expenses [Member]
Significant Transactions [Line Items]
Other operating and administrative expenses		237,000,000
NBCUniversal Enterprise Credit Facility [Member]
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	1,250,000,000
NBCUniversal Enterprise Credit Facility [Member] | NBCUniversal Media, LLC [Member]
Significant Transactions [Line Items]
Consideration transferred related to the Redemption Transaction and purchase of certain properties	$1,250,000,000

Related_Party_Transactions_Nar

Related Party Transactions (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Borrowing margin for LIBOR based borrowings	1.00%
Settlement Of Station Venture Liability	$0	$602,000,000	$0
Other noncurrent liabilities	10,819,000,000	11,384,000,000
NBCUniversal Media, LLC [Member]
Revolving Credit Agreement Capacity		3,000,000,000
Collateral Liability For Unconsolidated Subsidiary Debt		482,000,000
Borrowing margin for LIBOR based borrowings	1.00%
Settlement Of Station Venture Liability	0	602,000,000	0
Redemption transaction distribution	0	3,200,000,000	0
Other noncurrent liabilities	3,722,000,000	3,412,000,000
Nbcuniversal Holdings Preferred Stock [Member] | NBCUniversal Media, LLC [Member]
Preferred stock liquidition preference value	9,400,000,000
Preferred stock dividend rate percentage	8.25%
Carrying Value Of Related Party Contractual Obligation [Member] | NBCUniversal Media, LLC [Member]
Other noncurrent liabilities	$383,000,000	$383,000,000

Related_Party_Transactions_Con

Related Party Transactions - Consolidated Balance Sheet (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Receivables, net	$6,321	$6,376
Accounts payable and accrued expenses related to trade creditors	5,638	5,528
Accrued expenses and other current liabilities	5,293	7,967
Other noncurrent liabilities	10,819	11,384
NBCUniversal Media, LLC [Member]
Receivables, net	4,842	4,911
Accounts payable and accrued expenses related to trade creditors	1,388	1,583
Accrued expenses and other current liabilities	1,422	1,465
Note payable to Comcast	865	799
Other noncurrent liabilities	3,722	3,412
Transactions With Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media, LLC [Member]
Receivables, net	229	228
Accounts payable and accrued expenses related to trade creditors	47	56
Accrued expenses and other current liabilities	8	37
Note payable to Comcast	865	799
Other noncurrent liabilities	$383	$383

Related_Party_Transactions_Con1

Related Party Transactions - Consolidated Statement of Income (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$17,732,000,000	$16,791,000,000	$16,844,000,000	$17,408,000,000	$16,926,000,000	$16,151,000,000	$16,270,000,000	$15,310,000,000	$68,775,000,000	$64,657,000,000	$62,570,000,000
NBCUniversal Media, LLC [Member]
Revenue									25,428,000,000	23,650,000,000	23,812,000,000
Transactions With Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media, LLC [Member]
Revenue									1,315,000,000	1,262,000,000	1,228,000,000
Operating costs and expenses									-162,000,000	-190,000,000	-175,000,000
Other income (expense)									($43,000,000)	$0	$0

Film_and_Television_Costs_Film

Film and Television Costs (Film and Television Costs)(Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Film And Television Costs [Line Items]
Programming rights, less amortization	$2,157	$2,039
Total film costs, television costs and programming rights	6,566	5,922
Less: Current portion of programming rights	839	928
Film and television costs	5,727	4,994
NBCUniversal Media, LLC [Member]
Film And Television Costs [Line Items]
Programming rights, less amortization	2,130	2,003
Total film costs, television costs and programming rights	6,539	5,886
Less: Current portion of programming rights	825	903
Film and television costs	5,714	4,983
Film Costs [Member]
Film And Television Costs [Line Items]
Released, less amortization	1,371	1,630
Completed, not released	71	70
In production and in development	1,189	658
Total film costs	2,631	2,358
Film Costs [Member] | NBCUniversal Media, LLC [Member]
Film And Television Costs [Line Items]
Released, less amortization	1,371	1,630
Completed, not released	71	70
In production and in development	1,189	658
Total film costs	2,631	2,358
Television Costs [Member]
Film And Television Costs [Line Items]
Released, less amortization	1,273	1,155
In production and in development	505	370
Total television costs	1,778	1,525
Television Costs [Member] | NBCUniversal Media, LLC [Member]
Film And Television Costs [Line Items]
Released, less amortization	1,273	1,155
In production and in development	505	370
Total television costs	$1,778	$1,525

Film_and_Television_Costs_Narr

Film and Television Costs (Narrative)(Details) (USD $)	Dec. 31, 2014
Amortization of completed film and television production expected to be amortized during the next fiscal year	$1,300,000,000
Expected amortization percentage of released and unamortized film and television costs	86.00%
Remaining unamortized costs of acquired film and television libraries	570,000,000
Expected amortization percentage of unamortized film and television library costs during the next three fiscal years	51.00%
NBCUniversal Media, LLC [Member]
Amortization of completed film and television production expected to be amortized during the next fiscal year	1,300,000,000
Expected amortization percentage of released and unamortized film and television costs	86.00%
Remaining unamortized costs of acquired film and television libraries	$570,000,000
Expected amortization percentage of unamortized film and television library costs during the next three fiscal years	51.00%

Investments_Details

Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair value method	$662,000,000	$4,345,000,000
Equity method	1,019,000,000	989,000,000
Cost method	2,056,000,000	2,009,000,000
Total Investments	3,737,000,000	7,343,000,000
Less: Current investments	602,000,000	3,573,000,000
Noncurrent investments	3,135,000,000	3,770,000,000
NBCUniversal Media, LLC [Member]
Fair value method	10,000,000	11,000,000
Equity method	840,000,000	852,000,000
Cost method	32,000,000	21,000,000
Total Investments	882,000,000	884,000,000
Other Equity Method Investments [Member]
Equity method	517,000,000	469,000,000
Other Equity Method Investments [Member] | NBCUniversal Media, LLC [Member]
Equity method	338,000,000	332,000,000
Air Touch [Member]
Cost method	1,568,000,000	1,553,000,000
Other Investment [Member]
Cost method	488,000,000	456,000,000
The Weather Channel [Member]
Equity method	335,000,000	333,000,000
The Weather Channel [Member] | NBCUniversal Media, LLC [Member]
Equity method	335,000,000	333,000,000
Hulu [Member]
Equity method	167,000,000	187,000,000
Hulu [Member] | NBCUniversal Media, LLC [Member]
Equity method	$167,000,000	$187,000,000

Investments_Investment_Income_

Investments (Investment Income (Loss), Net) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Gains on sales and exchanges of investments, net	$192	$484	$30
Investment impairment losses	-50	-29	-24
Unrealized gains on securities underlying prepaid forward sale agreements	66	1,601	1,159
Mark to market adjustments on derivative component of prepaid forward sale agreements and indexed debt instruments	-56	-1,604	-1,071
Interest and dividend income	116	111	119
Other, net	28	13	6
Investment income (loss), net	296	576	219
NBCUniversal Media, LLC [Member]
Investment income (loss), net	$27	$17	$27

Investments_Fair_Value_Method_

Investments (Fair Value Method Investments) (Details) (USD $)	12 Months Ended
Share data in Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair value equity securities held as collateral	$523,000,000	$3,959,000,000
Obligations under prepaid forward sale agreements	119,000,000	811,000,000
Derivative component of prepaid forward sale agreements	356,000,000	2,800,000,000
Total liabilities associated with prepaid forward sale agreements	475,000,000	3,611,000,000
Fair Value Equity Securities Settlement	3,200,000,000	1,400,000,000
Proceeds From Sales Of Businesses And Investments	666,000,000	1,083,000,000	3,102,000,000
Clearwire LLC [Member]
Proceeds from sale of available-for-sale securities		443,000,000
Fair Value Investment Shares Sold		89
Pre-tax gain realized on Clearwire		443,000,000
Liberty Media Redemption Transaction [Member]
Shares Redeemed		6.3
Fair value of the shares delivered in the Liberty Media exchange transaction		937,000,000
Proceeds From Sales Of Businesses And Investments		$417,000,000

Investments_Equity_Method_Inve

Investments (Equity Method Investments) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Impairment of investment		$249,000,000
Return of capital from investees	25,000,000	149,000,000	2,362,000,000
NBCUniversal Media, LLC [Member]
Impairment of investment		249,000,000
The Weather Channel [Member]
Total distribution from investee		152,000,000
Return of capital from investees		128,000,000
The Weather Channel [Member] | NBCUniversal Media, LLC [Member]
Total distribution from investee		152,000,000
Return of capital from investees		128,000,000
Hulu [Member]
Capital contribution agreement		247,000,000
Hulu [Member] | NBCUniversal Media, LLC [Member]
Capital contribution agreement		$247,000,000

Investments_Cost_Method_Invest

Investments (Cost Method Investments) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Air Touch [Member]
Fair value of AirTouch preferred stock related to redeemable preferred shares	$1,700,000,000	$1,700,000,000
Aggregate redemption value	1,750,000,000
Carrying amount of redeemable preferred stock	1,600,000,000	1,500,000,000
Fair value of redeemable preferred stock	1,700,000,000	1,700,000,000
Nonredeemable preferred stock	100,000,000	100,000,000
Preferred Shares Redeemable in April 2020 [Member]
Aggregate redemption value	$1,650,000,000

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014
Cable distribution system	$30,498,000,000	$31,655,000,000
Customer premise equipment	25,949,000,000	27,086,000,000
Other equipment	6,826,000,000	7,860,000,000
Buildings and leasehold improvements	8,057,000,000	8,650,000,000
Land	1,084,000,000	1,112,000,000
Property and equipment, at cost	72,414,000,000	76,363,000,000
Less: Accumulated depreciation	42,574,000,000	45,410,000,000
Property and equipment, net	29,840,000,000	30,953,000,000
NBCUniversal Media, LLC [Member]
Buildings and leasehold improvements	5,239,000,000	5,780,000,000
Land	799,000,000	820,000,000
Furniture, fixtures and equipment	2,383,000,000	2,930,000,000
Construction in process	828,000,000	775,000,000
Property and equipment, at cost	9,249,000,000	10,305,000,000
Less: Accumulated depreciation	1,599,000,000	2,167,000,000
Property and equipment, net	7,650,000,000	8,138,000,000
Cable Distribution System [Member]
Weighted average original useful life (in years)		11
Customer Premise Equipment [Member]
Weighted average original useful life (in years)		6
Other Equipment [Member]
Weighted average original useful life (in years)		6
Buildings and Leasehold Improvements [Member]
Weighted average original useful life (in years)		22
Buildings and Leasehold Improvements [Member] | NBCUniversal Media, LLC [Member]
Weighted average original useful life (in years)		21
Furniture Fixtures And Equipment [Member] | NBCUniversal Media, LLC [Member]
Weighted average original useful life (in years)		7
Comcast Center [Member]
Equity interest acquired	80.00%
Acquisition Of Real Estate Properties [Member]
Increases in property and equpiment related to real estate acquisitions	2,200,000,000
Acquisition Of Real Estate Properties [Member] | NBCUniversal Media, LLC [Member]
Increases in property and equpiment related to real estate acquisitions	$1,700,000,000

Goodwill_Rollforward_Details

Goodwill Rollforward (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Goodwill beginning balance	$27,098,000,000	$26,985,000,000
Acquisitions	227,000,000	42,000,000
Adjustments	-9,000,000	71,000,000
Goodwill ending balance	27,316,000,000	27,098,000,000
NBCUniversal Media, LLC [Member]
Goodwill beginning balance	14,882,000,000	14,770,000,000
Acquisitions	35,000,000	42,000,000
Adjustments	-9,000,000	70,000,000
Goodwill ending balance	14,908,000,000	14,882,000,000
Cable Communications [Member]
Goodwill beginning balance	12,206,000,000	12,206,000,000
Acquisitions	11,000,000	0
Adjustments	0	0
Goodwill ending balance	12,217,000,000	12,206,000,000
Cable Networks [Member]
Goodwill beginning balance	13,130,000,000	13,026,000,000
Acquisitions	20,000,000	39,000,000
Adjustments	-202,000,000	65,000,000
Goodwill ending balance	12,948,000,000	13,130,000,000
Cable Networks [Member] | NBCUniversal Media, LLC [Member]
Goodwill beginning balance	13,130,000,000	13,026,000,000
Acquisitions	20,000,000	39,000,000
Adjustments	-202,000,000	65,000,000
Goodwill ending balance	12,948,000,000	13,130,000,000
Broadcast Television [Member]
Goodwill beginning balance	769,000,000	761,000,000
Acquisitions	0	3,000,000
Adjustments	-2,000,000	5,000,000
Goodwill ending balance	767,000,000	769,000,000
Broadcast Television [Member] | NBCUniversal Media, LLC [Member]
Goodwill beginning balance	769,000,000	761,000,000
Acquisitions	0	3,000,000
Adjustments	-2,000,000	5,000,000
Goodwill ending balance	767,000,000	769,000,000
Filmed Entertainment [Member]
Goodwill beginning balance	1,000,000	1,000,000
Acquisitions	15,000,000	0
Adjustments	195,000,000	0
Goodwill ending balance	211,000,000	1,000,000
Filmed Entertainment [Member] | NBCUniversal Media, LLC [Member]
Goodwill beginning balance	1,000,000	1,000,000
Acquisitions	15,000,000	0
Adjustments	195,000,000	0
Goodwill ending balance	211,000,000	1,000,000
Theme Parks [Member]
Goodwill beginning balance	982,000,000	982,000,000
Acquisitions	0	0
Adjustments	0	0
Goodwill ending balance	982,000,000	982,000,000
Theme Parks [Member] | NBCUniversal Media, LLC [Member]
Goodwill beginning balance	982,000,000	982,000,000
Acquisitions	0	0
Adjustments	0	0
Goodwill ending balance	982,000,000	982,000,000
Corporate and Other [Member]
Goodwill beginning balance	10,000,000	9,000,000
Acquisitions	181,000,000	0
Adjustments	0	1,000,000
Goodwill ending balance	$191,000,000	$10,000,000

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Intangible Assets) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Franchise rights	$59,364	$59,364
Accumulated amortization	-10,170	-8,874
Total	86,514	85,567
NBCUniversal Media, LLC [Member]
Accumulated amortization	-4,829	-4,003
Total	19,016	18,860
Trade names
Indefinite Lived Intangible Assets Excluding Goodwill	3,083	3,089
Trade names | NBCUniversal Media, LLC [Member]
Indefinite Lived Intangible Assets Excluding Goodwill	3,059	3,089
FCC Licenses
Indefinite Lived Intangible Assets Excluding Goodwill	651	652
FCC Licenses | NBCUniversal Media, LLC [Member]
Indefinite Lived Intangible Assets Excluding Goodwill	651	652
Customer relationships
Finite-lived intangible assets, gross carrying amount	15,129	15,037
Accumulated amortization	-5,495	-4,772
Weighted average original useful life	19 years 0 months 0 days
Customer relationships | NBCUniversal Media, LLC [Member]
Finite-lived intangible assets, gross carrying amount	13,093	13,086
Accumulated amortization	-3,636	-2,982
Weighted average original useful life	19 years 0 months 0 days
Cable franchise renewal costs and contractual operating rights
Finite-lived intangible assets, gross carrying amount	1,418	1,360
Accumulated amortization	-792	-745
Weighted average original useful life	10 years 0 months 0 days
Software
Finite-lived intangible assets, gross carrying amount	5,040	4,271
Accumulated amortization	-2,832	-2,405
Weighted average original useful life	5 years 0 months 0 days
Software | NBCUniversal Media, LLC [Member]
Finite-lived intangible assets, gross carrying amount	657	522
Accumulated amortization	-329	-240
Weighted average original useful life	5 years 0 months 0 days
Patents and other technology rights
Finite-lived intangible assets, gross carrying amount	373	361
Accumulated amortization	-330	-307
Weighted average original useful life	8 years 0 months 0 days
Other agreements and rights
Finite-lived intangible assets, gross carrying amount	1,456	1,433
Accumulated amortization	-721	-645
Weighted average original useful life	20 years 0 months 0 days
Other agreements and rights | NBCUniversal Media, LLC [Member]
Finite-lived intangible assets, gross carrying amount	1,556	1,511
Accumulated amortization	($864)	($781)
Weighted average original useful life	21 years 0 months 0 days

Goodwill_and_Other_Intangible_

Goodwill and Other Intangible Assets (Amortization of Intangible Assets) (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Future amortization expense, 2015	$1,619
Future amortization expense, 2016	1,457
Future amortization expense, 2017	1,296
Future amortization expense, 2018	1,053
Future amortization expense, 2019	842
NBCUniversal Media, LLC [Member]
Future amortization expense, 2015	777
Future amortization expense, 2016	748
Future amortization expense, 2017	747
Future amortization expense, 2018	743
Future amortization expense, 2019	$740

LongTerm_Debt_Details

Long-Term Debt (Details)

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

USD ($)

USD ($)

NBCUniversal Media, LLC [Member]

NBCUniversal Media, LLC [Member]

Revolving bank credit facility [Member]

Commercial Paper Program

Senior notes with maturities of 5 years or less [Member]

Senior notes with maturities of 5 years or less [Member]

Senior notes with maturities of 5 years or less [Member]

Senior notes with maturities of 5 years or less [Member]

Senior notes with maturities between 5 and 10 years [Member]

Senior notes with maturities between 5 and 10 years [Member]

Senior notes with maturities between 5 and 10 years [Member]

Senior notes with maturities between 5 and 10 years [Member]

Senior notes with maturities greater than 10 years [Member]

Senior notes with maturities greater than 10 years [Member]

Senior notes with maturities greater than 10 years [Member]

Senior notes with maturities greater than 10 years [Member]

Other Including Capital Lease Obligations [Member]

Other Including Capital Lease Obligations [Member]

Other Including Capital Lease Obligations [Member]

Other Including Capital Lease Obligations [Member]

Notes 5.50% Due 2029 [Member]

Notes 5.50% Due 2029 [Member]

Notes 5.50% Due 2029 [Member]

Notes 5.50% Due 2029 [Member]

USD ($)

USD ($)

USD ($)

USD ($)

NBCUniversal Media, LLC [Member]

NBCUniversal Media, LLC [Member]

USD ($)

USD ($)

NBCUniversal Media, LLC [Member]

NBCUniversal Media, LLC [Member]

USD ($)

USD ($)

NBCUniversal Media, LLC [Member]

NBCUniversal Media, LLC [Member]

USD ($)

USD ($)

NBCUniversal Media, LLC [Member]

NBCUniversal Media, LLC [Member]

USD ($)

GBP (£)

USD ($)

GBP (£)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Commercial paper

$845,000,000

$1,350,000,000

Revolving credit facilities

0

1,250,000,000

Senior notes

15,334,000,000

15,080,000,000

2,005,000,000

2,917,000,000

10,527,000,000

11,533,000,000

4,996,000,000

4,996,000,000

20,937,000,000

18,010,000,000

3,204,000,000

3,205,000,000

974,000,000

625,000,000

1,000,000,000

625,000,000

Other, including capital lease obligations

591,000,000

624,000,000

44,000,000

47,000,000

Total debt

48,234,000,000

47,847,000,000

10,249,000,000

11,165,000,000

Less: current portion

4,217,000,000

3,280,000,000

1,023,000,000

906,000,000

Long-term debt, less current portion

$44,017,000,000

$44,567,000,000

$9,226,000,000

$10,259,000,000

Weighted average interest rate

4.95%

4.46%

0.00%

0.37%

4.64%

3.25%

4.82%

4.39%

5.74%

5.61%

LongTerm_Debt_Debt_Maturities_

Long-Term Debt (Debt Maturities) (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
2015	$4,217
2016	3,530
2017	2,558
2018	4,117
2019	2,205
Thereafter	31,607
Weighted average interest rate	4.95%
NBCUniversal Media, LLC [Member]
2015	1,023
2016	1,008
2017	2
2018	2
2019	2
Thereafter	$8,212
2015
Weighted average interest rate	4.99%
2015 | NBCUniversal Media, LLC [Member]
Weighted average interest rate	3.63%
2016
Weighted average interest rate	4.16%
2016 | NBCUniversal Media, LLC [Member]
Weighted average interest rate	2.89%
2017
Weighted average interest rate	6.97%
2017 | NBCUniversal Media, LLC [Member]
Weighted average interest rate	6.30%
2018
Weighted average interest rate	4.12%
2018 | NBCUniversal Media, LLC [Member]
Weighted average interest rate	6.31%
2019
Weighted average interest rate	3.16%
2019 | NBCUniversal Media, LLC [Member]
Weighted average interest rate	6.33%
Thereafter [Member]
Weighted average interest rate	5.43%
Thereafter [Member] | NBCUniversal Media, LLC [Member]
Weighted average interest rate	4.87%

LongTerm_Debt_Debt_Borrowings_

Long-Term Debt (Debt Borrowings) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Senior 3.60% Notes Due 2024 [Member]
Principal amount	$1,200
Interest rate	3.60%
Maturity date	2024
Senior 4.75% Notes Due 2044 [Member]
Principal amount	1,000
Interest rate	4.75%
Maturity date	2044
Senior 4.200% Notes Due 2034 [Member]
Principal amount	1,000
Interest rate	4.20%
Maturity date	2034
Senior 3.375% Notes Due 2025 [Member]
Principal amount	1,000
Interest rate	3.38%
Maturity date	2025
Current Year Borrowings [Member]
Principal amount	$4,200

LongTerm_Debt_Debt_Repayments_

Long-Term Debt (Debt Repayments) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Repurchases and repayments of debt	$3,175,000,000	$2,444,000,000	$2,881,000,000
NBCUniversal Media, LLC [Member]
Repurchases and repayments of debt	906,000,000	92,000,000	413,000,000
NBCUniversal Enterprise Credit Facility [Member]
Repurchases and repayments of debt	1,250,000,000
Senior 5.3% Notes Due 2014 [Member]
Repurchases and repayments of debt	1,000,000,000
Interest rate	5.30%
Maturity date	2014
Senior 2.1% Notes Due 2014 [Member]
Repurchases and repayments of debt	900,000,000
Interest rate	2.10%
Maturity date	2014
Senior 2.1% Notes Due 2014 [Member] | NBCUniversal Media, LLC [Member]
Repurchases and repayments of debt	900,000,000
Interest rate	2.10%
Maturity date	2014
Other Long-Term Debt [Member]
Repurchases and repayments of debt	$25,000,000

LongTerm_Debt_Narrative_Detail

Long-Term Debt (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Long-term Debt, Fair Value	$55,300,000,000	$51,800,000,000
Borrowing margin for LIBOR based borrowings	1.00%
Amounts available under revolving credit facilities	6,500,000,000
Unused irrevocable standby letters of credit	473,000,000
Commercial paper	845,000,000	1,350,000,000
NBCUniversal Media, LLC [Member]
Long-term Debt, Fair Value	11,500,000,000	11,700,000,000
Comcast And Comcast Cable Communications LLC [Member]
Debt Instrument, Maturity Date, Description	Jun-17
Credit facility borrowing capacity	6,250,000,000
NBCUniversal Enterprise [Member] | NBCUniversal Media, LLC [Member]
Principal amount	4,000,000,000
Preferred stock liquidition preference value	725,000,000
NBCUniversal Enterprise Commercial Paper [Member]
Credit facility borrowing capacity	1,350,000,000
Comcast And Comcast Cable Revolving Credit Facility [Member] | NBCUniversal Media, LLC [Member]
Guarantee Obligations Current Principal Balance	6,250,000,000
Debt Instrument, Maturity Date, Description	Jun-17
Comcast And Comcast Cable Debt Securities [Member] | NBCUniversal Media, LLC [Member]
Guarantee Obligations Current Principal Balance	32,600,000,000
NBCUniversal Enterprise Credit Facility [Member]
Debt Instrument, Maturity Date, Description	Mar-18
Borrowing margin for LIBOR based borrowings	1.00%
Credit facility borrowing capacity	1,350,000,000
Amounts available under revolving credit facilities	505,000,000
NBCUniversal Enterprise Credit Facility [Member] | NBCUniversal Media, LLC [Member]
Credit facility borrowing capacity	$1,350,000,000

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Trading securities	$523	$3,956
Available-for-sale Securities	132	389
Interest rate swap agreements	84	110
Other [assets]	71	81
Fair Value, Assets Measured on Recurring Basis, Total	810	4,536
Derivative component of prepaid forward sale agreements and indexed debt instruments	361	2,816
Contractual Obligation	883	747
Contingent consideration	644	684
Other [liabilities]	8	16
Fair Value Liabilities Measured On Recurring Basis	1,896	4,263
Fair Value, Inputs, Level 1 [Member]
Trading securities	523	3,956
Available-for-sale Securities	1	260
Interest rate swap agreements	0	0
Other [assets]	0	0
Fair Value, Assets Measured on Recurring Basis, Total	524	4,216
Derivative component of prepaid forward sale agreements and indexed debt instruments	0	0
Contractual Obligation	0	0
Contingent consideration	0	0
Other [liabilities]	0	0
Fair Value Liabilities Measured On Recurring Basis	0	0
Fair Value, Inputs, Level 2 [Member]
Trading securities	0	0
Available-for-sale Securities	121	118
Interest rate swap agreements	84	110
Other [assets]	64	80
Fair Value, Assets Measured on Recurring Basis, Total	269	308
Derivative component of prepaid forward sale agreements and indexed debt instruments	361	2,816
Contractual Obligation	0	0
Contingent consideration	0	0
Other [liabilities]	8	16
Fair Value Liabilities Measured On Recurring Basis	369	2,832
Fair Value, Inputs, Level 3 [Member]
Trading securities	0	0
Available-for-sale Securities	10	11
Interest rate swap agreements	0	0
Other [assets]	7	1
Fair Value, Assets Measured on Recurring Basis, Total	17	12
Derivative component of prepaid forward sale agreements and indexed debt instruments	0	0
Contractual Obligation	883	747
Contingent consideration	644	684
Other [liabilities]	0	0
Fair Value Liabilities Measured On Recurring Basis	$1,527	$1,431

Fair_Value_Disclosure_Rollforw

Fair Value Disclosure Rollforward (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Nonrecurring fair value adjustments	$26	$167	$161
NBCUniversal Media, LLC [Member]
Nonrecurring fair value adjustments	26	167	161
Contractual Obligation [Member]
Beginning balance	747
Fair value adjustments	208
Payments	-72
Ending balance	883
Contractual Obligation [Member] | NBCUniversal Media, LLC [Member]
Beginning balance	747
Fair value adjustments	208
Payments	-72
Ending balance	883
Contingent Consideration [Member]
Beginning balance	684
Fair value adjustments	31
Payments	-71
Ending balance	$644
Maximum [Member]
Discount rate used to determine fair value	13.00%
Maximum [Member] | NBCUniversal Media, LLC [Member]
Discount rate used to determine fair value	13.00%
Minimum [Member]
Discount rate used to determine fair value	5.00%
Minimum [Member] | NBCUniversal Media, LLC [Member]
Discount rate used to determine fair value	12.00%

Pension_Plans_and_Postretireme1

Pension Plans and Postretirement Benefits (Narrative) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Severance costs	$152	$160	$155
Multiemployer Plans Funded Status	At least 80 percent
NBCUniversal Media, LLC [Member]
Severance costs	113	116	90
Multiemployer Plans Funded Status	At least 80 percent
Postretirement Benefits [Member]
Plan funded status	-837	-633	-703
Postretirement Benefits [Member] | NBCUniversal Media, LLC [Member]
Plan funded status	-209	-158	-177
Pension Benefits [Member]
Multiemployer plan contributions	58	59	40
Plan funded status	-339	-278	-402
Contribution to fully fund and settle plan		55
Reclassification adjustment from accumulated other comprehensive income before tax		74
Pension Benefits [Member] | NBCUniversal Media, LLC [Member]
Multiemployer plan contributions	58	59	40
Plan funded status	-339	-278	-329
Deferred Compensation Plans [Member]
Cash surrender value of life insurance policies	628	565
Retirement Investment Plans [Member]
Expenses related to retirement investment plans	379	324	246
Retirement Investment Plans [Member] | NBCUniversal Media, LLC [Member]
Expenses related to retirement investment plans	165	152	85
NBCUniversal Qualified Pension Plan [Member]
Plan funded status	16
NBCUniversal Qualified Pension Plan [Member] | NBCUniversal Media, LLC [Member]
Plan funded status	16
Benefit obligations in excess of plan assets	51	43
Postretirement and Other Benefits [Member]
Multiemployer plan contributions	125	98	114
Postretirement and Other Benefits [Member] | NBCUniversal Media, LLC [Member]
Multiemployer plan contributions	$125	$98	$114

Pension_Plans_and_Postretireme2

Pension Plans and Postretirement Benefits (Information On Our Pension Benefit Plans) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Benefit obligation	$581	$498	$805
Fair value of plan assets	242	220	403
Plan funded status and recorded benefit obligation	-339	-278	-402
Portion of benefit obligation not yet recognized in benefits expense	53	-3	151
Benefits expense	14	12	163
Expected return on plan assets	5.00%	5.00%	5.00%
Service cost			139
Pension Benefits [Member] | NBCUniversal Media, LLC [Member]
Benefit obligation	581	498	546
Fair value of plan assets	242	220	217
Plan funded status and recorded benefit obligation	-339	-278	-329
Portion of benefit obligation not yet recognized in benefits expense	53	-3	53
Benefits expense	14	12	142
Expected return on plan assets	5.00%	5.00%	5.00%
Service cost			134
Pension Benefits [Member] | Minimum [Member]
Discount rate	3.75%	4.50%	3.25%
Pension Benefits [Member] | Minimum [Member] | NBCUniversal Media, LLC [Member]
Discount rate	3.75%	4.50%	3.75%
Pension Benefits [Member] | Maximum [Member]
Discount rate	4.25%	5.25%	4.25%
Pension Benefits [Member] | Maximum [Member] | NBCUniversal Media, LLC [Member]
Discount rate	4.25%	5.25%	4.25%
Postretirement Benefits [Member]
Benefit obligation	837	633	703
Plan funded status and recorded benefit obligation	-837	-633	-703
Portion of benefit obligation not yet recognized in benefits expense	46	-110	17
Benefits expense	59	65	60
Discount rate	4.25%		4.25%
Postretirement Benefits [Member] | NBCUniversal Media, LLC [Member]
Benefit obligation	209	158	177
Plan funded status and recorded benefit obligation	-209	-158	-177
Portion of benefit obligation not yet recognized in benefits expense	-3	-44	-11
Benefits expense	$12	$14	$15
Discount rate	4.25%	5.25%	4.25%
Postretirement Benefits [Member] | Minimum [Member]
Discount rate		5.00%
Postretirement Benefits [Member] | Maximum [Member]
Discount rate		5.25%

Pension_Plans_and_Postretireme3

Pension Plans and Postretirement Benefits (Deferred Compensation Plans) (Details) (Deferred Compensation Plans [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Benefit obligation	$1,774	$1,434	$1,247
Interest expense	149	128	107
NBCUniversal Media, LLC [Member]
Benefit obligation	349	250	163
Interest expense	$24	$18	$11

Pension_Plans_and_Postretireme4

Pension Plans and Postretirement Benefits (Benefit Obligation and Expense for Our Split-Dollar Life Insurance Agreements) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Postretirement and Pension Plans
Benefit obligation	$217	$212	$202
Other operating and administrative expenses	$52	$50	$58

Equity_Narrative_Details

Equity (Narrative) (Details) (USD $)	12 Months Ended
In Billions, unless otherwise specified	Dec. 31, 2014
Number of votes entitled of each class B common stock	15
Availability remaining under share repurchase program	$3.25
Existing Authorization [Member]
Share repurchase authorization	7.5
New Authorization [Member]
Share repurchase authorization	$10
Class A Common Stock [Member]
Voting power	66.67%
Class B Common Stock [Member]
Voting power	33.33%

Equity_Changes_in_Common_Stock

Equity (Changes in Common Stock) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Repurchases and retirements of common stock	81,000,000	49,000,000	96,000,000
Class A Common Stock [Member]
Common Stock, Shares, Outstanding, Beginning Balance	2,138,075,133	2,122,000,000	2,095,000,000
Stock compensation plans	13,000,000	14,000,000	24,000,000
Repurchases and retirements of common stock	-22,000,000	0	0
Employee stock purchase plan	2,000,000	2,000,000	3,000,000
Common Stock, Shares, Outstanding, Ending Balance	2,131,137,862	2,138,075,133	2,122,000,000
Class A Special Common Stock [Member]
Common Stock, Shares, Outstanding, Beginning Balance	459,030,180	508,000,000	601,000,000
Stock compensation plans	0	0	3,000,000
Repurchases and retirements of common stock	-59,000,000	-49,000,000	-96,000,000
Employee stock purchase plan	0	0	0
Common Stock, Shares, Outstanding, Ending Balance	400,484,837	459,030,180	508,000,000
Class B Common Stock [Member]
Common Stock, Shares, Outstanding, Beginning Balance	9,444,375	9,000,000	9,000,000
Stock compensation plans	0	0	0
Repurchases and retirements of common stock	0	0	0
Employee stock purchase plan	0	0	0
Common Stock, Shares, Outstanding, Ending Balance	9,444,375	9,444,375	9,000,000

Equity_Aggregate_Share_Repurch

Equity (Aggregate Share Repurchases) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity
Cash consideration	$4,251	$2,000	$3,000
Shares repurchased	81	49	96

Equity_Components_of_Accumulat

Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Unrealized gains (losses) on marketable securities	$1,000,000	$67,000,000
Deferred gains (losses) on cash flow hedges	-4,000,000	-45,000,000
Unrecognized gains (losses) on employee benefit obligations	-68,000,000	71,000,000
Cumulative translation adjustments	-75,000,000	-37,000,000
Accumulated other comprehensive income (loss), net of deferred taxes	-146,000,000	56,000,000
NBCUniversal Media, LLC [Member]
Deferred gains (losses) on cash flow hedges	20,000,000	-5,000,000
Unrecognized gains (losses) on employee benefit obligations	-61,000,000	45,000,000
Cumulative translation adjustments	-118,000,000	-56,000,000
Accumulated other comprehensive income (loss), net of deferred taxes	($159,000,000)	($16,000,000)

ShareBased_Compensation_Narrat

Share-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income tax effects allocated directly to equity, other	$299	$244	$164
Share-based compensation arrangement by share-based payment award, award vesting period in years	5 years 0 months 0 days
NBCUniversal Media, LLC [Member]
Share-based compensation arrangement by share-based payment award, award vesting period in years	5 years 0 months 0 days
Stock Options [Member]
Unrecognized pretax compensation expense on nonvested awards	321
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 9 months 18 days
Period from grant date that an equity-based award expires	10 years 0 months 0 days
Stock Options [Member] | NBCUniversal Media, LLC [Member]
Unrecognized pretax compensation expense on nonvested awards	25
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	2 years 1 month 6 days
Period from grant date that an equity-based award expires	10 years 0 months 0 days
Restricted Share Units [Member]
Unrecognized pretax compensation expense on nonvested awards	505
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 8 months 12 days
Restricted Share Units [Member] | NBCUniversal Media, LLC [Member]
Unrecognized pretax compensation expense on nonvested awards	$124
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)	1 year 7 months 6 days

ShareBased_Compensation_Recogn

Share-Based Compensation (Recognized Share-Based Compensation Expense) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Recognized share-based compensation expense	$414	$334	$301
NBCUniversal Media, LLC [Member]
Recognized share-based compensation expense	91	62	47
Stock Options [Member]
Recognized share-based compensation expense	160	139	131
Stock Options [Member] | NBCUniversal Media, LLC [Member]
Recognized share-based compensation expense	16	15	15
Restricted Share Units [Member]
Recognized share-based compensation expense	231	175	154
Restricted Share Units [Member] | NBCUniversal Media, LLC [Member]
Recognized share-based compensation expense	69	42	28
Employee Stock Purchase Plan [Member]
Recognized share-based compensation expense	23	20	16
Employee Stock Purchase Plan [Member] | NBCUniversal Media, LLC [Member]
Recognized share-based compensation expense	$6	$5	$4

ShareBased_Compensation_Stock_

Share-Based Compensation (Stock Options and Restricted Share Units) (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014
Stock options granted	16
Weighted-average exercise price, granted	$50.03
Stock options outstanding	98
Weighted-average exercise price, outstanding	$30.29
RSUs granted	8
Nonvested restricted share units	24
Weighted-average fair value at grant date of nonvested RSUs	$34.11

ShareBased_Compensation_Restri

Share-Based Compensation (Restricted Share Units and Stock Option Fair Value) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Weighted average fair value of RSUs	$47.91	$38.28	$27.80
Fair value of stock options	$11.11	$8.80	$7.38
Dividend yield	1.80%	1.90%	2.20%
Expected volatility	24.00%	25.00%	29.00%
Risk-free interest rate	2.20%	1.30%	1.70%
Expected option life (in years)	6 years 6 months 0 days	7 years 0 months 0 days	7 years 0 months 0 days
NBCUniversal Media, LLC [Member]
Weighted average fair value of RSUs	$48.04	$37.79	$27.51
Fair value of stock options	$11.09	$8.86	$7.42
Dividend yield	1.80%	1.90%	2.20%
Expected volatility	24.00%	25.20%	29.00%
Risk-free interest rate	2.20%	1.30%	1.70%
Expected option life (in years)	6 years 6 months 0 days	7 years 0 months 0 days	7 years 0 months 0 days

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 19, 2013
Foreign income before taxes		$385,000,000	$524,000,000	$434,000,000
Liability for uncertain tax positions, noncurrent		1,200,000,000
Unrecognized tax benefits that would impact effective tax rate		603,000,000
Unrecognized tax benefits, interest on income taxes accrued		452,000,000	780,000,000
Change In Income Tax Expense Related To Effectively Settled Uncertain Tax Positions	724,000,000
Income Tax Effects Allocated Directly to Equity, Other		299,000,000	244,000,000	164,000,000
Deferred income taxes, total		32,959,000,000	31,935,000,000
Franchise Rights [Member]
Net deferred tax liability, franchise rights		23,000,000,000
Uncertain Tax Positions Indemnified By GE [Member]
Liability for uncertain tax positions, noncurrent		243,000,000
Unrecognized tax benefits, interest on income taxes accrued		44,000,000	42,000,000
Redemption Transaction [Member]
Deferred income taxes, total					1,600,000,000
Other Acquisitions [Member]
Business Acquisition Purchase Price Allocation Deferred Income Taxes Asset Liability Net1		26,000,000
Other Comprehensive Income (Loss) [Member]
Income Tax Effects Allocated Directly to Equity, Other		127,000,000
Domestic Tax Authority
Operating loss carryforwards		127,000,000
Operating loss carryforwards expiration dates		31-Dec-34
Foreign Tax Authority
Operating loss carryforwards		$331,000,000
Operating loss carryforwards expiration dates		31-Dec-24

Income_Taxes_Components_of_Inc

Income Taxes (Components of Income Tax Expense) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Federal	$2,392	$3,183	$3,004
State	174	581	432
Foreign	142	200	169
Current income tax expense (benefit)	2,708	3,964	3,605
Federal	1,000	-76	160
State	173	108	-40
Foreign deferred income tax expense	-8	-16	19
Deferred income tax expense (benefit)	1,165	16	139
Income tax expense	3,873	3,980	3,744
NBCUniversal Media, LLC [Member]
Foreign	33	77	69
Foreign deferred income tax expense	-8	-16	16
Deferred income tax expense (benefit)	-12	-10	15
Withholding tax expense	108	123	103
U.S. domestic tax expense	10	22	9
Income tax expense	$143	$206	$197

Income_Taxes_Federal_Statutory

Income Taxes (Federal Statutory) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Federal tax at statutory rate	$4,363	$3,890	$4,063
State income taxes, net of federal benefit	329	319	178
Foreign income taxes, net of federal credit	0	15	92
Nontaxable income attributable to noncontrolling interests	-62	-103	-620
Other adjustments	-114	-313	-106
Income tax expense	3,873	3,980	3,744
Uncertain And Effectively Settled Tax Positions, Net [Member]
Other adjustments	-408	58	114
Accrued Interest On Uncertain And Effectively Settled Tax Positions Net [Member]
Other adjustments	($235)	$114	$23

Income_Taxes_Components_of_Net

Income Taxes (Components of Net Deferred Tax Liability) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Net operating loss carryforwards	$448	$495
Differences between book and tax basis of long-term debt	116	117
Nondeductible accruals and other	3,383	3,588
Less: Valuation allowance	375	405
Total deferred tax assets	3,572	3,795
Total deferred tax liabilities	36,336	35,494
Net deferred tax liability	32,764	31,699
Property And Equipment And Intangible Assets [Member]
Deferred tax liabilities, other	35,112	34,044
Investments [Member]
Deferred tax liabilities, other	186	473
Indexed Debt Securities [Member]
Deferred tax liabilities, other	534	610
Foreign Subsidiaries And Undistributed Foreign Earnings [Member]
Deferred tax liabilities, other	$504	$367

Income_Taxes_Reconciliation_of

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Beginning balance	$1,701	$1,573	$1,435
Additions based on tax positions related to the current year	63	90	154
Additions based on tax positions related to prior years	111	201	79
Additions from acquired subsidiaries	0	268	0
Reductions for tax positions of prior years	-220	-141	-60
Reductions due to expiration of statutes of limitations	-448	-3	-3
Settlements with taxing authorities	-36	-287	-32
Ending balance	$1,171	$1,701	$1,573

Supplemental_Financial_Informa2

Supplemental Financial Information (Receivables)(Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Receivables, gross	$6,885,000,000	$6,972,000,000
Less: Allowance for returns and customer incentives	359,000,000	375,000,000
Less: Allowance for doubtful accounts	205,000,000	221,000,000
Receivables, net	6,321,000,000	6,376,000,000
Noncurrent receivables, net	569,000,000	488,000,000
NBCUniversal Media, LLC [Member]
Receivables, gross	5,258,000,000	5,348,000,000
Less: Allowance for returns and customer incentives	356,000,000	372,000,000
Less: Allowance for doubtful accounts	60,000,000	65,000,000
Receivables, net	4,842,000,000	4,911,000,000
Noncurrent receivables, net	$569,000,000	$488,000,000

Supplemental_Financial_Informa3

Supplemental Financial Information (Components of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Unrealized gains (losses) on marketable securities	$1,000,000	$67,000,000
Deferred gains (losses) on cash flow hedges	-4,000,000	-45,000,000
Unrecognized gains (losses) on employee benefit obligations	-68,000,000	71,000,000
Cumulative translation adjustments	-75,000,000	-37,000,000
Accumulated other comprehensive income (loss), net of deferred taxes	-146,000,000	56,000,000
NBCUniversal Media, LLC [Member]
Deferred gains (losses) on cash flow hedges	20,000,000	-5,000,000
Unrecognized gains (losses) on employee benefit obligations	-61,000,000	45,000,000
Cumulative translation adjustments	-118,000,000	-56,000,000
Accumulated other comprehensive income (loss), net of deferred taxes	($159,000,000)	($16,000,000)

Supplemental_Financial_Informa4

Supplemental Financial Information (Cash Payments for Interest and Income Taxes)(Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest	$2,389	$2,355	$2,314
Income taxes	3,668	3,946	2,841
NBCUniversal Media, LLC [Member]
Interest	485	462	461
Income taxes	$174	$205	$169

Supplemental_Financial_Informa5

Supplemental Financial Information (Noncash Investing and Financing Activities)(Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 19, 2013
Noncontrolling Interest Acquired				49.00%
Purchase of NBCUniversal noncontrolling interest		$16,700,000,000
Consideration transferred related to the Redemption Transaction and purchase of certain properties		725,000,000
Total noncash consideration transferred related to the Redemption Transaction		6,000,000,000
Dividends payable, amount	572,000,000	509,000,000	430,000,000
Dividends payable, amount per share	$0.23	$0.20	$0.16
Capital expenditures incurred but not yet paid	797,000,000	872,000,000	757,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired			85,000,000
Fair Value Equity Securities Settlement	3,200,000,000	1,400,000,000
NBCUniversal Media, LLC [Member]
Capital expenditures incurred but not yet paid	148,000,000	306,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired			85,000,000
Revolving Credit Facility Member
Consideration transferred related to the Redemption Transaction and purchase of certain properties		1,250,000,000
NBCUniversal Enterprise Senior Unsecured Debt Securities [Member]
Consideration transferred related to the Redemption Transaction and purchase of certain properties		4,000,000,000
NBCUniversal Enterprise Preferred Stock [Member]
Consideration transferred related to the Redemption Transaction and purchase of certain properties		$725,000,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Narrative) (Details)	Dec. 31, 2014
	numberofemployees
Number of employees covered under collective bargaining agreements	7,400
Percentage of employees covered under collective bargaining agreements that have expired or are scheduled to expire during 2015	30.00%
NBCUniversal Media, LLC [Member]
Number of employees covered under collective bargaining agreements	7,400
Percentage of employees covered under collective bargaining agreements that have expired or are scheduled to expire during 2015	30.00%

Commitments_and_Contingencies_2

Commitments and Contingencies (Minimum Annual Commitments under the Programming License Agreements and Operating Leases) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Programming and talent commitments future minimum payments, 2015	$4,915
Programming and talent commitments future minimum payments, 2016	4,657
Programming and talent commitments future minimum payments, 2017	3,177
Programming and talent commitments future minimum payments, 2018	3,999
Programming and talent commitments future minimum payments, 2019	2,793
Programming and talent commitments future minimum payments, thereafter	26,130
Operating leases future minimum payments, 2015	399
Operating leases future minimum payments, 2016	359
Operating leases future minimum payments, 2017	299
Operating leases future minimum payments, 2018	253
Operating leases future minimum payments, 2019	197
Operating leases future minimum payments, thereafter	754
NBCUniversal Media, LLC [Member]
Programming and talent commitments future minimum payments, 2015	4,898
Programming and talent commitments future minimum payments, 2016	4,648
Programming and talent commitments future minimum payments, 2017	3,173
Programming and talent commitments future minimum payments, 2018	3,998
Programming and talent commitments future minimum payments, 2019	2,793
Programming and talent commitments future minimum payments, thereafter	26,130
Operating leases future minimum payments, 2015	150
Operating leases future minimum payments, 2016	135
Operating leases future minimum payments, 2017	107
Operating leases future minimum payments, 2018	89
Operating leases future minimum payments, 2019	73
Operating leases future minimum payments, thereafter	$402

Commitments_and_Contingencies_3

Commitments and Contingencies (Rental expense) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Rent expense	$580	$616	$688
NBCUniversal Media, LLC [Member]
Rent expense	$222	$250	$317

Financial_Data_by_Business_Seg2

Financial Data by Business Segment (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$17,732,000,000	$16,791,000,000	$16,844,000,000	$17,408,000,000	$16,926,000,000	$16,151,000,000	$16,270,000,000	$15,310,000,000	$68,775,000,000	$64,657,000,000	$62,570,000,000
Operating income (loss) before depreciation and amortization									22,923,000,000	21,434,000,000	19,977,000,000
Depreciation and amortization									8,019,000,000	7,871,000,000	7,798,000,000
Operating income (loss)	3,787,000,000	3,745,000,000	3,804,000,000	3,568,000,000	3,647,000,000	3,414,000,000	3,435,000,000	3,067,000,000	14,904,000,000	13,563,000,000	12,179,000,000
Capital expenditures									7,420,000,000	6,596,000,000	5,714,000,000
Assets	159,339,000,000				158,813,000,000				159,339,000,000	158,813,000,000
NBCUniversal Media, LLC [Member]
Revenue									25,428,000,000	23,650,000,000	23,812,000,000
Operating income (loss) before depreciation and amortization									5,588,000,000	4,732,000,000	4,107,000,000
Depreciation and amortization									1,495,000,000	1,411,000,000	1,326,000,000
Operating income (loss)									4,093,000,000	3,321,000,000	2,781,000,000
Capital expenditures									1,221,000,000	1,160,000,000	763,000,000
Assets	52,617,000,000				51,739,000,000				52,617,000,000	51,739,000,000
Non U S Customers [Member]
Revenue									4,400,000,000	4,800,000,000	4,500,000,000
Non U S Customers [Member] | NBCUniversal Media, LLC [Member]
Revenue									4,433,000,000	4,763,000,000	4,464,000,000
United States [Member] | NBCUniversal Media, LLC [Member]
Revenue									20,995,000,000	18,887,000,000	19,348,000,000
Cable Communications [Member]
Revenue									44,140,000,000	41,836,000,000	39,604,000,000
Operating income (loss) before depreciation and amortization									18,112,000,000	17,205,000,000	16,255,000,000
Depreciation and amortization									6,422,000,000	6,394,000,000	6,405,000,000
Operating income (loss)									11,690,000,000	10,811,000,000	9,850,000,000
Capital expenditures									6,154,000,000	5,403,000,000	4,921,000,000
Cable segment revenue types as percentage of total cable revenue									100.00%	100.00%	100.00%
Assets	140,616,000,000				132,082,000,000				140,616,000,000	132,082,000,000
Cable Networks [Member]
Revenue									9,563,000,000	9,201,000,000	8,727,000,000
Operating income (loss) before depreciation and amortization									3,589,000,000	3,501,000,000	3,303,000,000
Depreciation and amortization									748,000,000	734,000,000	735,000,000
Operating income (loss)									2,841,000,000	2,767,000,000	2,568,000,000
Capital expenditures									49,000,000	67,000,000	150,000,000
Assets	28,582,000,000				29,413,000,000				28,582,000,000	29,413,000,000
Cable Networks [Member] | NBCUniversal Media, LLC [Member]
Revenue									9,563,000,000	9,201,000,000	8,727,000,000
Operating income (loss) before depreciation and amortization									3,589,000,000	3,501,000,000	3,303,000,000
Depreciation and amortization									748,000,000	734,000,000	735,000,000
Operating income (loss)									2,841,000,000	2,767,000,000	2,568,000,000
Capital expenditures									49,000,000	67,000,000	150,000,000
Assets	28,582,000,000				29,413,000,000				28,582,000,000	29,413,000,000
Broadcast Television [Member]
Revenue									8,542,000,000	7,120,000,000	8,200,000,000
Operating income (loss) before depreciation and amortization									734,000,000	345,000,000	358,000,000
Depreciation and amortization									127,000,000	98,000,000	97,000,000
Operating income (loss)									607,000,000	247,000,000	261,000,000
Capital expenditures									76,000,000	65,000,000	65,000,000
Assets	6,806,000,000				6,723,000,000				6,806,000,000	6,723,000,000
Broadcast Television [Member] | NBCUniversal Media, LLC [Member]
Revenue									8,542,000,000	7,120,000,000	8,200,000,000
Operating income (loss) before depreciation and amortization									734,000,000	345,000,000	358,000,000
Depreciation and amortization									127,000,000	98,000,000	97,000,000
Operating income (loss)									607,000,000	247,000,000	261,000,000
Capital expenditures									76,000,000	65,000,000	65,000,000
Assets	6,806,000,000				6,723,000,000				6,806,000,000	6,723,000,000
Filmed Entertainment [Member]
Revenue									5,008,000,000	5,452,000,000	5,159,000,000
Operating income (loss) before depreciation and amortization									711,000,000	483,000,000	79,000,000
Depreciation and amortization									21,000,000	15,000,000	16,000,000
Operating income (loss)									690,000,000	468,000,000	63,000,000
Capital expenditures									11,000,000	9,000,000	7,000,000
Assets	4,185,000,000				3,549,000,000				4,185,000,000	3,549,000,000
Filmed Entertainment [Member] | NBCUniversal Media, LLC [Member]
Revenue									5,008,000,000	5,452,000,000	5,159,000,000
Operating income (loss) before depreciation and amortization									711,000,000	483,000,000	79,000,000
Depreciation and amortization									21,000,000	15,000,000	16,000,000
Operating income (loss)									690,000,000	468,000,000	63,000,000
Capital expenditures									11,000,000	9,000,000	7,000,000
Assets	4,185,000,000				3,549,000,000				4,185,000,000	3,549,000,000
Theme Parks [Member]
Revenue									2,623,000,000	2,235,000,000	2,085,000,000
Operating income (loss) before depreciation and amortization									1,168,000,000	1,004,000,000	953,000,000
Depreciation and amortization									273,000,000	300,000,000	268,000,000
Operating income (loss)									895,000,000	704,000,000	685,000,000
Capital expenditures									671,000,000	580,000,000	272,000,000
Assets	7,017,000,000				6,608,000,000				7,017,000,000	6,608,000,000
Theme Parks [Member] | NBCUniversal Media, LLC [Member]
Revenue									2,623,000,000	2,235,000,000	2,085,000,000
Operating income (loss) before depreciation and amortization									1,168,000,000	1,004,000,000	953,000,000
Depreciation and amortization									273,000,000	300,000,000	268,000,000
Operating income (loss)									895,000,000	704,000,000	685,000,000
Capital expenditures									671,000,000	580,000,000	272,000,000
Assets	7,017,000,000				6,608,000,000				7,017,000,000	6,608,000,000
Headquarters And Other [Member]
Revenue									13,000,000	31,000,000	43,000,000
Operating income (loss) before depreciation and amortization									-613,000,000	-588,000,000	-603,000,000
Depreciation and amortization									326,000,000	264,000,000	210,000,000
Operating income (loss)									-939,000,000	-852,000,000	-813,000,000
Capital expenditures									414,000,000	439,000,000	269,000,000
Assets	6,479,000,000				6,002,000,000				6,479,000,000	6,002,000,000
Headquarters And Other [Member] | NBCUniversal Media, LLC [Member]
Revenue									13,000,000	31,000,000	43,000,000
Operating income (loss) before depreciation and amortization									-613,000,000	-588,000,000	-603,000,000
Depreciation and amortization									326,000,000	264,000,000	210,000,000
Operating income (loss)									-939,000,000	-852,000,000	-813,000,000
Capital expenditures									414,000,000	439,000,000	269,000,000
Assets	6,479,000,000				6,002,000,000				6,479,000,000	6,002,000,000
NBCUniversal Eliminations [Member]
Revenue									-321,000,000	-389,000,000	-402,000,000
Operating income (loss) before depreciation and amortization									-1,000,000	-13,000,000	17,000,000
Depreciation and amortization									0	0	0
Operating income (loss)									-1,000,000	-13,000,000	17,000,000
Capital expenditures									0	0	0
Assets	-452,000,000				-556,000,000				-452,000,000	-556,000,000
NBCUniversal Eliminations [Member] | NBCUniversal Media, LLC [Member]
Revenue									-321,000,000	-389,000,000	-402,000,000
Operating income (loss) before depreciation and amortization									-1,000,000	-13,000,000	17,000,000
Depreciation and amortization									0	0	0
Operating income (loss)									-1,000,000	-13,000,000	17,000,000
Capital expenditures									0	0	0
Assets	-452,000,000				-556,000,000				-452,000,000	-556,000,000
NBCUniversal [Member]
Revenue									25,428,000,000	23,650,000,000	23,812,000,000
Operating income (loss) before depreciation and amortization									5,588,000,000	4,732,000,000	4,107,000,000
Depreciation and amortization									1,495,000,000	1,411,000,000	1,326,000,000
Operating income (loss)									4,093,000,000	3,321,000,000	2,781,000,000
Capital expenditures									1,221,000,000	1,160,000,000	763,000,000
Assets	52,617,000,000				51,739,000,000				52,617,000,000	51,739,000,000
Corporate and Other [Member]
Revenue									709,000,000	600,000,000	498,000,000
Operating income (loss) before depreciation and amortization									-778,000,000	-489,000,000	-376,000,000
Depreciation and amortization									102,000,000	66,000,000	67,000,000
Operating income (loss)									-880,000,000	-555,000,000	-443,000,000
Capital expenditures									45,000,000	33,000,000	30,000,000
Assets	5,338,000,000				8,152,000,000				5,338,000,000	8,152,000,000
Eliminations [Member]
Revenue									-1,502,000,000	-1,429,000,000	-1,344,000,000
Operating income (loss) before depreciation and amortization									1,000,000	-14,000,000	-9,000,000
Depreciation and amortization									0	0	0
Operating income (loss)									1,000,000	-14,000,000	-9,000,000
Capital expenditures									0	0	0
Assets	($39,232,000,000)				($33,160,000,000)				($39,232,000,000)	($33,160,000,000)
Cable Communications Segment Revenue Percentage-Video [Member]
Cable segment revenue types as percentage of total cable revenue									47.10%	49.10%	50.40%
Cable Communications Segment Revenue Percentage - High-speed Internet [Member]
Cable segment revenue types as percentage of total cable revenue									25.60%	24.70%	24.10%
Cable Communications Segment Revenue Percentage- Voice [Member]
Cable segment revenue types as percentage of total cable revenue									8.30%	8.70%	9.00%
Cable Communications Segment Revenue Percentage- Business Services [Member]
Cable segment revenue types as percentage of total cable revenue									9.00%	7.70%	6.50%
Cable Communications Segment Revenue Percentage- Advertising [Member]
Cable segment revenue types as percentage of total cable revenue									5.50%	5.20%	5.80%
Cable Communications Segment Revenue Percentage- Other [Member]
Cable segment revenue types as percentage of total cable revenue									4.50%	4.60%	4.20%
Cable Communications Segment Revenue Percentage- Franchise and other regulatory fees [Member]
Cable segment revenue types as percentage of total cable revenue									2.80%	2.80%	2.80%

Quarterly_Financial_Informatio2

Quarterly Financial Information (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure Abstract
Revenue	$17,732	$16,791	$16,844	$17,408	$16,926	$16,151	$16,270	$15,310	$68,775	$64,657	$62,570
Operating income	3,787	3,745	3,804	3,568	3,647	3,414	3,435	3,067	14,904	13,563	12,179
Net income attributable to Parent	1,925	2,592	1,992	1,871	1,913	1,732	1,734	1,437	8,380	6,816	6,203
Basic earnings per common share attributable to Comcast Corporation shareholders	$0.75	$1	$0.77	$0.72	$0.73	$0.66	$0.66	$0.55	$3.24	$2.60	$2.32
Diluted earnings per common share attributable to Comcast Corporation shareholders	$0.74	$0.99	$0.76	$0.71	$0.72	$0.65	$0.65	$0.54	$3.20	$2.56	$2.28
Dividends declared per common share	$0.23	$0.23	$0.23	$0.23	$0.20	$0.20	$0.20	$0.20	$0.90	$0.78	$0.65
Change In Income Tax Expense Related To Effectively Settled Uncertain Tax Positions		$724

Condensed_Consolidating_Financ2

Condensed Consolidating Financial Information (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Comcast Holdings' ZONES due October 2029 [Member]
Debt Instrument, Maturity Date, Description	Oct-29
Principal amount of debt securities subject to guarantee	$185,000,000
Comcast Holdings' ZONES due November 2029 [Member]
Debt Instrument, Maturity Date, Description	Nov-29
Principal amount of debt securities not subject to guarantee	62,000,000
Guarantor Subsidiaries [Member]
Principal amount of debt securities subject to guarantee	32,600,000,000
Maturing In Next Five Years [Member]
Principal amount of debt securities subject to guarantee	9,300,000,000
NBCUniversal Enterprise Credit Facility [Member]
Debt Instrument, Maturity Date, Description	Mar-18
Credit facility borrowing capacity	1,350,000,000
Comcast And Comcast Cable Communications LLC [Member]
Debt Instrument, Maturity Date, Description	Jun-17
Credit facility borrowing capacity	6,250,000,000
NBCUniversal Enterprise [Member]
Principal amount of debt securities subject to guarantee	$4,000,000,000

Condensed_Consolidating_Financ3

Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheet) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash and cash equivalents	$3,910,000,000	$1,718,000,000	$10,951,000,000	$1,620,000,000
Investments [Current]	602,000,000	3,573,000,000
Receivables, net	6,321,000,000	6,376,000,000
Programming rights	839,000,000	928,000,000
Other current assets	1,859,000,000	1,480,000,000
Total current assets	13,531,000,000	14,075,000,000
Film and television costs	5,727,000,000	4,994,000,000
Investments	3,135,000,000	3,770,000,000
Property and equipment, net	30,953,000,000	29,840,000,000
Franchise rights	59,364,000,000	59,364,000,000
Goodwill	27,316,000,000	27,098,000,000	26,985,000,000
Other intangible assets, net	16,980,000,000	17,329,000,000
Other noncurrent assets, net	2,333,000,000	2,343,000,000
Total assets	159,339,000,000	158,813,000,000
Accounts payable and accrued expenses related to trade creditors	5,638,000,000	5,528,000,000
Accrued participations and residuals	1,347,000,000	1,239,000,000
Accrued expenses and other current liabilities [condensed]	6,208,000,000	8,865,000,000
Current portion of long-term debt	4,217,000,000	3,280,000,000
Total current liabilities	17,410,000,000	18,912,000,000
Long-term debt, less current portion	44,017,000,000	44,567,000,000
Deferred income taxes	32,959,000,000	31,935,000,000
Other noncurrent liabilities	10,819,000,000	11,384,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,066,000,000	957,000,000
Common stock	30,000,000	30,000,000
Other shareholders' equity	52,681,000,000	50,664,000,000
Total Comcast Corporation shareholders' equity	52,711,000,000	50,694,000,000
Noncontrolling interests	357,000,000	364,000,000
Total equity	53,068,000,000	51,058,000,000	49,796,000,000	47,655,000,000
Total liabilities and equity	159,339,000,000	158,813,000,000
Elimination and Consolidation Adjustments [Member]
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	-495,953,000,000	-460,590,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	-1,080,000,000	-882,000,000
Total assets	-497,033,000,000	-461,472,000,000
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	-936,000,000	-741,000,000
Other noncurrent liabilities	-144,000,000	-141,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	-495,953,000,000	-460,590,000,000
Total Comcast Corporation shareholders' equity	-495,953,000,000	-460,590,000,000
Noncontrolling interests	0	0
Total equity	-495,953,000,000	-460,590,000,000
Total liabilities and equity	-497,033,000,000	-461,472,000,000
Comcast Parent [Member]
Cash and cash equivalents	0	0	0	0
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	267,000,000	237,000,000
Total current assets	267,000,000	237,000,000
Film and television costs	0	0
Investments	36,000,000	11,000,000
Investments in and amounts due from subsidiaries eliminated upon consolidation	84,142,000,000	79,956,000,000
Property and equipment, net	199,000,000	220,000,000
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	11,000,000	11,000,000
Other noncurrent assets, net	1,224,000,000	1,078,000,000
Total assets	85,879,000,000	81,513,000,000
Accounts payable and accrued expenses related to trade creditors	19,000,000	8,000,000
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	1,547,000,000	1,371,000,000
Current portion of long-term debt	1,650,000,000	2,351,000,000
Total current liabilities	3,216,000,000	3,730,000,000
Long-term debt, less current portion	27,616,000,000	25,170,000,000
Deferred income taxes	0	0
Other noncurrent liabilities	2,336,000,000	1,919,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	30,000,000	30,000,000
Other shareholders' equity	52,681,000,000	50,664,000,000
Total Comcast Corporation shareholders' equity	52,711,000,000	50,694,000,000
Noncontrolling interests	0	0
Total equity	52,711,000,000	50,694,000,000
Total liabilities and equity	85,879,000,000	81,513,000,000
Comcast Holdings [Member]
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	103,420,000,000	97,429,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	148,000,000	145,000,000
Total assets	103,568,000,000	97,574,000,000
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	283,000,000	266,000,000
Current portion of long-term debt	0	0
Total current liabilities	283,000,000	266,000,000
Long-term debt, less current portion	126,000,000	132,000,000
Deferred income taxes	701,000,000	777,000,000
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	102,458,000,000	96,399,000,000
Total Comcast Corporation shareholders' equity	102,458,000,000	96,399,000,000
Noncontrolling interests	0	0
Total equity	102,458,000,000	96,399,000,000
Total liabilities and equity	103,568,000,000	97,574,000,000
CCCL Parent [Member]
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	110,323,000,000	102,673,000,000
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	110,323,000,000	102,673,000,000
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	233,000,000	180,000,000
Current portion of long-term debt	0	0
Total current liabilities	233,000,000	180,000,000
Long-term debt, less current portion	1,827,000,000	1,827,000,000
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	108,263,000,000	100,666,000,000
Total Comcast Corporation shareholders' equity	108,263,000,000	100,666,000,000
Noncontrolling interests	0	0
Total equity	108,263,000,000	100,666,000,000
Total liabilities and equity	110,323,000,000	102,673,000,000
Combined CCHMO Parents [Member]
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	58,677,000,000	54,724,000,000
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	58,677,000,000	54,724,000,000
Accounts payable and accrued expenses related to trade creditors	1,000,000	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	47,000,000	47,000,000
Current portion of long-term debt	677,000,000	0
Total current liabilities	725,000,000	47,000,000
Long-term debt, less current portion	822,000,000	1,505,000,000
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	57,130,000,000	53,172,000,000
Total Comcast Corporation shareholders' equity	57,130,000,000	53,172,000,000
Noncontrolling interests	0	0
Total equity	57,130,000,000	53,172,000,000
Total liabilities and equity	58,677,000,000	54,724,000,000
NBCUniversal Media Parent [Member]
Cash and cash equivalents	385,000,000	336,000,000	5,129,000,000	238,000,000
Investments [Current]	0	0
Receivables, net	0	0
Programming rights	0	0
Other current assets	41,000,000	35,000,000
Total current assets	426,000,000	371,000,000
Film and television costs	0	0
Investments	378,000,000	374,000,000
Investments in and amounts due from subsidiaries eliminated upon consolidation	41,239,000,000	40,644,000,000
Property and equipment, net	0	0
Franchise rights	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets, net	92,000,000	103,000,000
Total assets	42,135,000,000	41,492,000,000
Accounts payable and accrued expenses related to trade creditors	0	0
Accrued participations and residuals	0	0
Accrued expenses and other current liabilities [condensed]	331,000,000	323,000,000
Current portion of long-term debt	1,006,000,000	903,000,000
Total current liabilities	1,337,000,000	1,226,000,000
Long-term debt, less current portion	9,218,000,000	10,236,000,000
Deferred income taxes	67,000,000	59,000,000
Other noncurrent liabilities	1,143,000,000	931,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	0	0
Common stock	0	0
Other shareholders' equity	30,370,000,000	29,040,000,000
Total Comcast Corporation shareholders' equity	30,370,000,000	29,040,000,000
Noncontrolling interests	0	0
Total equity	30,370,000,000	29,040,000,000
Total liabilities and equity	42,135,000,000	41,492,000,000
Comcast Non-Guarantor Subsidiaries [Member]
Cash and cash equivalents	3,525,000,000	1,382,000,000	5,822,000,000	1,382,000,000
Investments [Current]	602,000,000	3,573,000,000
Receivables, net	6,321,000,000	6,376,000,000
Programming rights	839,000,000	928,000,000
Other current assets	1,551,000,000	1,208,000,000
Total current assets	12,838,000,000	13,467,000,000
Film and television costs	5,727,000,000	4,994,000,000
Investments	2,721,000,000	3,385,000,000
Investments in and amounts due from subsidiaries eliminated upon consolidation	98,152,000,000	85,164,000,000
Property and equipment, net	30,754,000,000	29,620,000,000
Franchise rights	59,364,000,000	59,364,000,000
Goodwill	27,316,000,000	27,098,000,000
Other intangible assets, net	16,969,000,000	17,318,000,000
Other noncurrent assets, net	1,949,000,000	1,899,000,000
Total assets	255,790,000,000	242,309,000,000
Accounts payable and accrued expenses related to trade creditors	5,618,000,000	5,520,000,000
Accrued participations and residuals	1,347,000,000	1,239,000,000
Accrued expenses and other current liabilities [condensed]	3,767,000,000	6,678,000,000
Current portion of long-term debt	884,000,000	26,000,000
Total current liabilities	11,616,000,000	13,463,000,000
Long-term debt, less current portion	4,408,000,000	5,697,000,000
Deferred income taxes	33,127,000,000	31,840,000,000
Other noncurrent liabilities	7,484,000,000	8,675,000,000
Redeemable noncontrolling interests and redeemable subsidiary preferred stock	1,066,000,000	957,000,000
Common stock	0	0
Other shareholders' equity	197,732,000,000	181,313,000,000
Total Comcast Corporation shareholders' equity	197,732,000,000	181,313,000,000
Noncontrolling interests	357,000,000	364,000,000
Total equity	198,089,000,000	181,677,000,000
Total liabilities and equity	$255,790,000,000	$242,309,000,000

Condensed_Consolidating_Financ4

Condensed Consolidating Financial Information (Condensed Consolidating Statement of Income) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Service revenue									$68,775,000,000	$64,657,000,000	$62,570,000,000
Revenue	17,732,000,000	16,791,000,000	16,844,000,000	17,408,000,000	16,926,000,000	16,151,000,000	16,270,000,000	15,310,000,000	68,775,000,000	64,657,000,000	62,570,000,000
Programming and production									20,912,000,000	19,670,000,000	19,929,000,000
Other operating and administrative									19,862,000,000	18,584,000,000	17,833,000,000
Advertising, marketing and promotion									5,078,000,000	4,969,000,000	4,831,000,000
Depreciation									6,337,000,000	6,254,000,000	6,150,000,000
Amortization									1,682,000,000	1,617,000,000	1,648,000,000
Costs and expenses, total									53,871,000,000	51,094,000,000	50,391,000,000
Operating income (loss)	3,787,000,000	3,745,000,000	3,804,000,000	3,568,000,000	3,647,000,000	3,414,000,000	3,435,000,000	3,067,000,000	14,904,000,000	13,563,000,000	12,179,000,000
Interest expense									-2,617,000,000	-2,574,000,000	-2,521,000,000
Investment income (loss), net									296,000,000	576,000,000	219,000,000
Equity in net income (losses) of investees, net									97,000,000	-86,000,000	959,000,000
Other income (expense), net									-215,000,000	-364,000,000	773,000,000
Nonoperating income (Expense), Total									-2,439,000,000	-2,448,000,000	-570,000,000
Income (loss) before income taxes									12,465,000,000	11,115,000,000	11,609,000,000
Income tax (expense) benefit									-3,873,000,000	-3,980,000,000	-3,744,000,000
Net income (loss)									8,592,000,000	7,135,000,000	7,865,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									-212,000,000	-319,000,000	-1,662,000,000
Net income (loss) attributable to Parent	1,925,000,000	2,592,000,000	1,992,000,000	1,871,000,000	1,913,000,000	1,732,000,000	1,734,000,000	1,437,000,000	8,380,000,000	6,816,000,000	6,203,000,000
Comprehensive income attributable to Parent									8,178,000,000	6,883,000,000	6,370,000,000
Elimination and Consolidation Adjustments [Member]
Service revenue									0	0	0
Management fee revenue									-2,450,000,000	-2,319,000,000	-2,191,000,000
Revenue									-2,450,000,000	-2,319,000,000	-2,191,000,000
Programming and production									0	0	0
Other operating and administrative									-2,450,000,000	-2,319,000,000	-2,191,000,000
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Costs and expenses, total									-2,450,000,000	-2,319,000,000	-2,191,000,000
Operating income (loss)									0	0	0
Interest expense									0	0	0
Investment income (loss), net									0	0	0
Equity in net income (losses) of investees, net									-40,417,000,000	-33,251,000,000	-32,425,000,000
Other income (expense), net									0	0	0
Nonoperating income (Expense), Total									-40,417,000,000	-33,251,000,000	-32,425,000,000
Income (loss) before income taxes									-40,417,000,000	-33,251,000,000	-32,425,000,000
Income tax (expense) benefit									0	0	0
Net income (loss)									-40,417,000,000	-33,251,000,000	-32,425,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net income (loss) attributable to Parent									-40,417,000,000	-33,251,000,000	-32,425,000,000
Comprehensive income attributable to Parent									-40,178,000,000	-33,175,000,000	-32,575,000,000
Comcast Parent [Member]
Service revenue									0	0	0
Management fee revenue									947,000,000	897,000,000	848,000,000
Revenue									947,000,000	897,000,000	848,000,000
Programming and production									0	0	0
Other operating and administrative									751,000,000	403,000,000	401,000,000
Advertising, marketing and promotion									0	0	0
Depreciation									34,000,000	30,000,000	30,000,000
Amortization									6,000,000	5,000,000	4,000,000
Costs and expenses, total									791,000,000	438,000,000	435,000,000
Operating income (loss)									156,000,000	459,000,000	413,000,000
Interest expense									-1,621,000,000	-1,523,000,000	-1,430,000,000
Investment income (loss), net									3,000,000	0	8,000,000
Equity in net income (losses) of investees, net									9,330,000,000	7,509,000,000	6,858,000,000
Other income (expense), net									0	-2,000,000	2,000,000
Nonoperating income (Expense), Total									7,712,000,000	5,984,000,000	5,438,000,000
Income (loss) before income taxes									7,868,000,000	6,443,000,000	5,851,000,000
Income tax (expense) benefit									512,000,000	373,000,000	352,000,000
Net income (loss)									8,380,000,000	6,816,000,000	6,203,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net income (loss) attributable to Parent									8,380,000,000	6,816,000,000	6,203,000,000
Comprehensive income attributable to Parent									8,178,000,000	6,883,000,000	6,370,000,000
Comcast Holdings [Member]
Service revenue									0	0	0
Management fee revenue									0	0	0
Revenue									0	0	0
Programming and production									0	0	0
Other operating and administrative									0	0	0
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Costs and expenses, total									0	0	0
Operating income (loss)									0	0	0
Interest expense									-11,000,000	-11,000,000	-23,000,000
Investment income (loss), net									12,000,000	-13,000,000	3,000,000
Equity in net income (losses) of investees, net									8,843,000,000	7,540,000,000	6,536,000,000
Other income (expense), net									0	0	0
Nonoperating income (Expense), Total									8,844,000,000	7,516,000,000	6,516,000,000
Income (loss) before income taxes									8,844,000,000	7,516,000,000	6,516,000,000
Income tax (expense) benefit									0	9,000,000	7,000,000
Net income (loss)									8,844,000,000	7,525,000,000	6,523,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net income (loss) attributable to Parent									8,844,000,000	7,525,000,000	6,523,000,000
Comprehensive income attributable to Parent									8,807,000,000	7,521,000,000	6,523,000,000
CCCL Parent [Member]
Service revenue									0	0	0
Management fee revenue									921,000,000	874,000,000	827,000,000
Revenue									921,000,000	874,000,000	827,000,000
Programming and production									0	0	0
Other operating and administrative									921,000,000	874,000,000	827,000,000
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Costs and expenses, total									921,000,000	874,000,000	827,000,000
Operating income (loss)									0	0	0
Interest expense									-176,000,000	-212,000,000	-329,000,000
Investment income (loss), net									0	0	0
Equity in net income (losses) of investees, net									8,273,000,000	7,430,000,000	6,665,000,000
Other income (expense), net									0	2,000,000	0
Nonoperating income (Expense), Total									8,097,000,000	7,220,000,000	6,336,000,000
Income (loss) before income taxes									8,097,000,000	7,220,000,000	6,336,000,000
Income tax (expense) benefit									62,000,000	73,000,000	115,000,000
Net income (loss)									8,159,000,000	7,293,000,000	6,451,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net income (loss) attributable to Parent									8,159,000,000	7,293,000,000	6,451,000,000
Comprehensive income attributable to Parent									8,162,000,000	7,276,000,000	6,460,000,000
Combined CCHMO Parents [Member]
Service revenue									0	0	0
Management fee revenue									582,000,000	548,000,000	516,000,000
Revenue									582,000,000	548,000,000	516,000,000
Programming and production									0	0	0
Other operating and administrative									582,000,000	548,000,000	516,000,000
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Costs and expenses, total									582,000,000	548,000,000	516,000,000
Operating income (loss)									0	0	0
Interest expense									-118,000,000	-126,000,000	-135,000,000
Investment income (loss), net									0	0	0
Equity in net income (losses) of investees, net									6,333,000,000	5,473,000,000	4,909,000,000
Other income (expense), net									0	0	0
Nonoperating income (Expense), Total									6,215,000,000	5,347,000,000	4,774,000,000
Income (loss) before income taxes									6,215,000,000	5,347,000,000	4,774,000,000
Income tax (expense) benefit									41,000,000	44,000,000	47,000,000
Net income (loss)									6,256,000,000	5,391,000,000	4,821,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net income (loss) attributable to Parent									6,256,000,000	5,391,000,000	4,821,000,000
Comprehensive income attributable to Parent									6,257,000,000	5,392,000,000	4,821,000,000
NBCUniversal Media Parent [Member]
Service revenue									0	0	0
Management fee revenue									0	0	0
Revenue									0	0	0
Programming and production									0	0	0
Other operating and administrative									908,000,000	855,000,000	899,000,000
Advertising, marketing and promotion									0	0	0
Depreciation									0	0	0
Amortization									0	0	0
Costs and expenses, total									908,000,000	855,000,000	899,000,000
Operating income (loss)									-908,000,000	-855,000,000	-899,000,000
Interest expense									-479,000,000	-488,000,000	-430,000,000
Investment income (loss), net									-7,000,000	3,000,000	5,000,000
Equity in net income (losses) of investees, net									4,523,000,000	3,331,000,000	4,402,000,000
Other income (expense), net									-4,000,000	-1,000,000	-14,000,000
Nonoperating income (Expense), Total									4,033,000,000	2,845,000,000	3,963,000,000
Income (loss) before income taxes									3,125,000,000	1,990,000,000	3,064,000,000
Income tax (expense) benefit									-10,000,000	-22,000,000	-9,000,000
Net income (loss)									3,115,000,000	1,968,000,000	3,055,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									0	0	0
Net income (loss) attributable to Parent									3,115,000,000	1,968,000,000	3,055,000,000
Comprehensive income attributable to Parent									2,972,000,000	2,017,000,000	3,068,000,000
Comcast Non-Guarantor Subsidiaries [Member]
Service revenue									68,775,000,000	64,657,000,000	62,570,000,000
Management fee revenue									0	0	0
Revenue									68,775,000,000	64,657,000,000	62,570,000,000
Programming and production									20,912,000,000	19,670,000,000	19,929,000,000
Other operating and administrative									19,150,000,000	18,223,000,000	17,381,000,000
Advertising, marketing and promotion									5,078,000,000	4,969,000,000	4,831,000,000
Depreciation									6,303,000,000	6,224,000,000	6,120,000,000
Amortization									1,676,000,000	1,612,000,000	1,644,000,000
Costs and expenses, total									53,119,000,000	50,698,000,000	49,905,000,000
Operating income (loss)									15,656,000,000	13,959,000,000	12,665,000,000
Interest expense									-212,000,000	-214,000,000	-174,000,000
Investment income (loss), net									288,000,000	586,000,000	203,000,000
Equity in net income (losses) of investees, net									3,212,000,000	1,882,000,000	4,014,000,000
Other income (expense), net									-211,000,000	-363,000,000	785,000,000
Nonoperating income (Expense), Total									3,077,000,000	1,891,000,000	4,828,000,000
Income (loss) before income taxes									18,733,000,000	15,850,000,000	17,493,000,000
Income tax (expense) benefit									-4,478,000,000	-4,457,000,000	-4,256,000,000
Net income (loss)									14,255,000,000	11,393,000,000	13,237,000,000
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock									-212,000,000	-319,000,000	-1,662,000,000
Net income (loss) attributable to Parent									14,043,000,000	11,074,000,000	11,575,000,000
Comprehensive income attributable to Parent									$13,980,000,000	$10,969,000,000	$11,703,000,000

Condensed_Consolidating_Financ5

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	-1,223,000,000	-297,000,000
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	4,182,000,000	2,933,000,000	4,544,000,000
Repurchases and repayments of debt	-3,175,000,000	-2,444,000,000	-2,881,000,000
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	-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

Schedule_II_Valuation_and_Qual2

Schedule II Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$221	$198	$202
Additions Charged to Costs and Expenses	162	317	293
Deductions from Reserves	178	294	297
Balance at End of Year	205	221	198
Allowance for Doubtful Accounts [Member] | NBCUniversal Media, LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	65	46	34
Additions Charged to Costs and Expenses	11	33	19
Deductions from Reserves	16	14	7
Balance at End of Year	60	65	46
Sales Returns and Allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	375	307	425
Additions Charged to Costs and Expenses	932	811	663
Deductions from Reserves	948	743	781
Balance at End of Year	359	375	307
Sales Returns and Allowances [Member] | NBCUniversal Media, LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	372	307	425
Additions Charged to Costs and Expenses	930	808	663
Deductions from Reserves	946	743	781
Balance at End of Year	356	372	307
Deferred Tax Valuation Allowance
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	405	355	297
Additions Charged to Costs and Expenses	33	71	61
Deductions from Reserves	63	21	3
Balance at End of Year	375	405	355
Deferred Tax Valuation Allowance | NBCUniversal Media, LLC [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	60	73	53
Additions Charged to Costs and Expenses	33	8	23
Deductions from Reserves	6	21	3
Balance at End of Year	$87	$60	$73