Consolidated Statement of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue	$ 84,526	$ 80,403	$ 74,510
Costs and Expenses:
Programming and production	25,384	24,463	22,550
Other operating and administrative	25,013	23,416	21,325
Advertising, marketing and promotion	6,317	6,107	5,957
Depreciation	7,914	7,464	6,781
Amortization	2,353	2,094	1,899
Other operating gains	(442)	0	0
Total costs and expenses	66,539	63,544	58,512
Operating income	17,987	16,859	15,998
Other Income (Expense):
Interest expense	(3,086)	(2,942)	(2,702)
Investment income (loss), net	253	213	81
Equity in net income (losses) of investees, net	107	(104)	(325)
Other income (expense), net	61	327	320
Total other income (expense)	(2,665)	(2,506)	(2,626)
Income before income taxes	15,322	14,353	13,372
Income tax benefit (expense)	7,578	(5,308)	(4,959)
Net income	22,900	9,045	8,413
Net (income) loss attributable to noncontrolling interests and redeemable subsidiary preferred stock	(186)	(350)	(250)
Net income attributable to Comcast Corporation	$ 22,714	$ 8,695	$ 8,163
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 4.82	$ 1.80	$ 1.64
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	4.75	1.78	1.62
Dividends declared per common share (in dollars per share)	$ 0.63	$ 0.55	$ 0.50
NBCUniversal Media LLC [Member]
Revenue	$ 32,997	$ 31,593	$ 28,462
Costs and Expenses:
Programming and production	14,304	14,540	13,418
Other operating and administrative	7,709	7,059	5,891
Advertising, marketing and promotion	2,799	2,767	2,795
Depreciation	994	861	669
Amortization	1,047	944	870
Other operating gains	(337)	0	0
Total costs and expenses	26,516	26,171	23,643
Operating income	6,481	5,422	4,819
Other Income (Expense):
Interest expense	(727)	(595)	(495)
Investment income (loss), net	46	30	5
Equity in net income (losses) of investees, net	(201)	(99)	(376)
Other income (expense), net	11	93	(102)
Total other income (expense)	(871)	(571)	(968)
Income before income taxes	5,610	4,851	3,851
Income tax benefit (expense)	(392)	(305)	(227)
Net income	5,218	4,546	3,624
Net (income) loss attributable to noncontrolling interests	(134)	(311)	(210)
Net income attributable to Comcast Corporation	$ 5,084	$ 4,235	$ 3,414