Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 352	$ 288	$ 250
Additions Charged to Costs and Expenses	769	616	554
Deductions from Reserves	702	552	516
Balance at End of Year	419	352	288
Allowance for doubtful accounts [Member] | NBCUniversal Media LLC [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	99	88	84
Additions Charged to Costs and Expenses	48	32	23
Deductions from Reserves	47	21	19
Balance at End of Year	100	99	88
Valuation allowance on deferred tax assets [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	632	377	266
Additions Charged to Costs and Expenses	1,403	367	111
Deductions from Reserves	129	112	0
Balance at End of Year	1,906	632	377
Valuation allowance on deferred tax assets [Member] | NBCUniversal Media LLC [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	73	87	72
Additions Charged to Costs and Expenses	36	13	15
Deductions from Reserves	15	27	0
Balance at End of Year	$ 94	$ 73	$ 87