Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating Activities
Net cash provided by (used in) operating activities			$ 13,497	$ 13,813
Investing Activities
Net transactions with affiliates			0	0
Capital expenditures	$ (2,406)	$ (2,165)	(6,562)	(5,862)
Cash paid for intangible assets			(1,163)	(916)
Acquisitions and construction of real estate properties			(303)	(116)
Acquisitions, net of cash acquired			(3,904)	(286)
Proceeds from sales of businesses and investments			188	420
Purchases of investments			(618)	(712)
Deposits			(1,761)	0
Other			(29)	268
Net cash provided by (used in) investing activities			(14,152)	(7,204)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			610	(220)
Proceeds from borrowings			9,231	3,996
Repurchases and repayments of debt			(2,994)	(4,353)
Repurchases and retirements of common stock			(3,762)	(5,770)
Dividends paid			(1,944)	(1,823)
Issuances of common stock			23	35
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			(194)	(178)
Other			197	(313)
Net cash provided by (used in) financing activities			1,167	(8,626)
Increase (decrease) in cash and cash equivalents			512	(2,017)
Cash and cash equivalents, beginning of period			2,295	3,910
Cash and cash equivalents, end of period	2,807	1,893	2,807	1,893
Elimination and Consolidation Adjustments [Member]
Operating Activities
Net cash provided by (used in) operating activities			0	0
Investing Activities
Net transactions with affiliates			0	0
Capital expenditures			0	0
Cash paid for intangible assets			0	0
Acquisitions and construction of real estate properties			0	0
Acquisitions, net of cash acquired			0	0
Proceeds from sales of businesses and investments			0	0
Purchases of investments			0	0
Deposits			0
Other			0	0
Net cash provided by (used in) investing activities			0	0
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			0	0
Proceeds from borrowings			0	0
Repurchases and repayments of debt			0	0
Repurchases and retirements of common stock			0	0
Dividends paid			0	0
Issuances of common stock			0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			0	0
Other			0	0
Net cash provided by (used in) financing activities			0	0
Increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			0	0
Cash and cash equivalents, end of period	0	0	0	0
Comcast Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities			(1,129)	(725)
Investing Activities
Net transactions with affiliates			(1,746)	6,786
Capital expenditures			(9)	(19)
Cash paid for intangible assets			(4)	(3)
Acquisitions and construction of real estate properties			(2)	0
Acquisitions, net of cash acquired			0	0
Proceeds from sales of businesses and investments			0	0
Purchases of investments			(23)	(3)
Deposits			0
Other			(108)	7
Net cash provided by (used in) investing activities			(1,892)	6,768
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			105	0
Proceeds from borrowings			9,231	3,996
Repurchases and repayments of debt			(750)	(2,650)
Repurchases and retirements of common stock			(3,762)	(5,770)
Dividends paid			(1,944)	(1,823)
Issuances of common stock			23	35
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			0	0
Other			118	169
Net cash provided by (used in) financing activities			3,021	(6,043)
Increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			0	0
Cash and cash equivalents, end of period	0	0	0	0
Comcast Holdings [Member]
Operating Activities
Net cash provided by (used in) operating activities			0	51
Investing Activities
Net transactions with affiliates			0	(51)
Capital expenditures			0	0
Cash paid for intangible assets			0	0
Acquisitions and construction of real estate properties			0	0
Acquisitions, net of cash acquired			0	0
Proceeds from sales of businesses and investments			0	0
Purchases of investments			0	0
Deposits			0
Other			0	0
Net cash provided by (used in) investing activities			0	(51)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			0	0
Proceeds from borrowings			0	0
Repurchases and repayments of debt			0	0
Repurchases and retirements of common stock			0	0
Dividends paid			0	0
Issuances of common stock			0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			0	0
Other			0	0
Net cash provided by (used in) financing activities			0	0
Increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			0	0
Cash and cash equivalents, end of period	0	0	0	0
CCCL Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities			(179)	(24)
Investing Activities
Net transactions with affiliates			179	697
Capital expenditures			0	0
Cash paid for intangible assets			0	0
Acquisitions and construction of real estate properties			0	0
Acquisitions, net of cash acquired			0	0
Proceeds from sales of businesses and investments			0	0
Purchases of investments			0	0
Deposits			0
Other			0	0
Net cash provided by (used in) investing activities			179	697
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			0	0
Proceeds from borrowings			0	0
Repurchases and repayments of debt			0	(673)
Repurchases and retirements of common stock			0	0
Dividends paid			0	0
Issuances of common stock			0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			0	0
Other			0	0
Net cash provided by (used in) financing activities			0	(673)
Increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			0	0
Cash and cash equivalents, end of period	0	0	0	0
NBCUniversal Media Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities			(1,068)	(1,019)
Investing Activities
Net transactions with affiliates			2,150	2,249
Capital expenditures			0	0
Cash paid for intangible assets			0	0
Acquisitions and construction of real estate properties			0	0
Acquisitions, net of cash acquired			0	0
Proceeds from sales of businesses and investments			104	1
Purchases of investments			(9)	(400)
Deposits			0
Other			(35)	(5)
Net cash provided by (used in) investing activities			2,210	1,845
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			0	0
Proceeds from borrowings			0	0
Repurchases and repayments of debt			(1,005)	(1,002)
Repurchases and retirements of common stock			0	0
Dividends paid			0	0
Issuances of common stock			0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			0	0
Other			25	0
Net cash provided by (used in) financing activities			(980)	(1,002)
Increase (decrease) in cash and cash equivalents			162	(176)
Cash and cash equivalents, beginning of period			414	385
Cash and cash equivalents, end of period	576	209	576	209
Comcast Non-Guarantor Subsidiaries [Member]
Operating Activities
Net cash provided by (used in) operating activities			15,873	15,530
Investing Activities
Net transactions with affiliates			(583)	(9,681)
Capital expenditures			(6,553)	(5,843)
Cash paid for intangible assets			(1,159)	(913)
Acquisitions and construction of real estate properties			(301)	(116)
Acquisitions, net of cash acquired			(3,904)	(286)
Proceeds from sales of businesses and investments			84	419
Purchases of investments			(586)	(309)
Deposits			(1,761)
Other			114	266
Net cash provided by (used in) investing activities			(14,649)	(16,463)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			505	(220)
Proceeds from borrowings			0	0
Repurchases and repayments of debt			(1,239)	(28)
Repurchases and retirements of common stock			0	0
Dividends paid			0	0
Issuances of common stock			0	0
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			(194)	(178)
Other			54	(482)
Net cash provided by (used in) financing activities			(874)	(908)
Increase (decrease) in cash and cash equivalents			350	(1,841)
Cash and cash equivalents, beginning of period			1,881	3,525
Cash and cash equivalents, end of period	$ 2,231	$ 1,684	$ 2,231	$ 1,684