Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 2,224	$ 3,632
Unrealized gains (losses) on marketable securities, net of deferred taxes	1	1
Deferred gains (losses) on cash flow hedges, net of deferred taxes	54	(59)
Amounts reclassified to net income:
Realized (gains) losses on cash flow hedges, net of deferred taxes	(106)	58
Employee benefit obligations, net of deferred taxes	(8)	(7)
Currency translation adjustments, net of deferred taxes	(2,157)	807
Comprehensive income	8	4,432
Less: Net income (loss) attributable to noncontrolling interests and redeemable subsidiary preferred stock	77	79
Less: Other comprehensive income (loss) attributable to noncontrolling interests	(25)	10
Comprehensive income (loss) attributable to Comcast Corporation	$ (44)	$ 4,343