Condensed Consolidated Statement of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Revenue	$ 27,205	$ 26,609
Costs and Expenses:
Programming and production	8,919	8,301
Other operating and administrative	8,269	8,254
Advertising, marketing and promotion	1,616	1,938
Depreciation	2,117	2,107
Amortization	1,245	1,157
Total costs and expenses	22,166	21,757
Operating income	5,039	4,852
Interest expense	(1,018)	(1,212)
Investment and other income (loss), net	390	(716)
Income before income taxes	4,411	2,924
Income tax expense	(1,119)	(700)
Net income	3,292	2,224
Less: Net income (loss) attributable to noncontrolling interests and redeemable subsidiary preferred stock	(37)	77
Net income attributable to Comcast Corporation	$ 3,329	$ 2,147
Basic earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 0.73	$ 0.47
Diluted earnings per common share attributable to Comcast Corporation shareholders (in dollars per share)	$ 0.71	$ 0.46