Condensed Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 3,630	$ 3,009	$ 6,922	$ 5,233
Currency translation adjustments, net of deferred taxes of $(17), $(9), $(109) and $(16)	61	(74)	26	(2,231)
Cash flow hedges:
Deferred gains (losses), net of deferred taxes of $2, $7, $(17) and $17	(14)	(27)	105	27
Realized (gains) losses reclassified to net income, net of deferred taxes of $—, $4, $— and $21	4	(21)	4	(127)
Employee benefit obligations and other, net of deferred taxes of $3, $3, $5 and $6	(7)	(11)	(17)	(18)
Comprehensive income	3,674	2,876	7,040	2,884
Less: Net income (loss) attributable to noncontrolling interests and redeemable subsidiary preferred stock	(108)	21	(145)	98
Less: Other comprehensive income (loss) attributable to noncontrolling interests	24	2	10	(23)
Comprehensive income (loss) attributable to Comcast Corporation	$ 3,758	$ 2,853	$ 7,175	$ 2,809