Condensed Consolidating Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating Activities
Net cash provided by (used in) operating activities			$ 9,383	$ 8,834
Investing Activities
Net transactions with affiliates			0	0
Capital expenditures	$ (2,271)	$ (1,971)	(4,156)	(3,697)
Cash paid for intangible assets			(737)	(600)
Acquisitions and construction of real estate properties			(211)	(65)
Acquisitions, net of cash acquired			(126)	(179)
Proceeds from sales of businesses and investments			138	395
Purchases of investments			(580)	(272)
Other			(156)	182
Net cash provided by (used in) investing activities			(5,828)	(4,236)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			205	(137)
Proceeds from borrowings			4,753	3,996
Repurchases and repayments of debt			(2,551)	(3,666)
Repurchases and retirements of common stock			(2,385)	(3,585)
Dividends paid			(1,281)	(1,200)
Issuances of common stock			19	32
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			(125)	(114)
Other			180	(348)
Net cash provided by (used in) financing activities			(1,185)	(5,022)
Increase (decrease) in cash and cash equivalents			2,370	(424)
Cash and cash equivalents, beginning of period			2,295	3,910
Cash and cash equivalents, end of period	4,665	3,486	4,665	3,486
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
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			(778)	(398)
Investing Activities
Net transactions with affiliates			880	3,661
Capital expenditures			(7)	(13)
Cash paid for intangible assets			(3)	(1)
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			(15)	(2)
Other			(164)	7
Net cash provided by (used in) investing activities			691	3,652
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			(400)	0
Proceeds from borrowings			4,753	3,996
Repurchases and repayments of debt			(750)	(2,650)
Repurchases and retirements of common stock			(2,385)	(3,585)
Dividends paid			(1,281)	(1,200)
Issuances of common stock			19	32
Distributions to noncontrolling interests and dividends for redeemable subsidiary preferred stock			0	0
Other			131	153
Net cash provided by (used in) financing activities			87	(3,254)
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	(1)
Investing Activities
Net transactions with affiliates			0	1
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
Other			0	0
Net cash provided by (used in) investing activities			0	1
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			(84)	(109)
Investing Activities
Net transactions with affiliates			84	109
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
Other			0	0
Net cash provided by (used in) investing activities			84	109
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
NBCUniversal Media Parent [Member]
Operating Activities
Net cash provided by (used in) operating activities			(809)	(751)
Investing Activities
Net transactions with affiliates			1,579	1,670
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			102	1
Purchases of investments			(2)	0
Other			(35)	(5)
Net cash provided by (used in) investing activities			1,644	1,666
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			0	0
Proceeds from borrowings			0	0
Repurchases and repayments of debt			(1,004)	(1,001)
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			(979)	(1,001)
Increase (decrease) in cash and cash equivalents			(144)	(86)
Cash and cash equivalents, beginning of period			414	385
Cash and cash equivalents, end of period	270	299	270	299
Comcast Non-Guarantor Subsidiaries [Member]
Operating Activities
Net cash provided by (used in) operating activities			11,054	10,093
Investing Activities
Net transactions with affiliates			(2,543)	(5,441)
Capital expenditures			(4,149)	(3,684)
Cash paid for intangible assets			(734)	(599)
Acquisitions and construction of real estate properties			(211)	(65)
Acquisitions, net of cash acquired			(126)	(179)
Proceeds from sales of businesses and investments			36	394
Purchases of investments			(563)	(270)
Other			43	180
Net cash provided by (used in) investing activities			(8,247)	(9,664)
Financing Activities
Proceeds from (repayments of) short-term borrowings, net			605	(137)
Proceeds from borrowings			0	0
Repurchases and repayments of debt			(797)	(15)
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			(125)	(114)
Other			24	(501)
Net cash provided by (used in) financing activities			(293)	(767)
Increase (decrease) in cash and cash equivalents			2,514	(338)
Cash and cash equivalents, beginning of period			1,881	3,525
Cash and cash equivalents, end of period	$ 4,395	$ 3,187	$ 4,395	$ 3,187