Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 95,743	$ 88,386
Less: Accumulated depreciation	51,306	49,916
Property and equipment, net	44,437	38,470
NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	18,183	15,512
Less: Accumulated depreciation	4,994	4,166
Property and equipment, net	$ 13,189	11,346
Cable Distribution System [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	11 years
Property and equipment, at cost	$ 38,380	36,046
Customer Premise Equipment [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	6 years
Property and equipment, at cost	$ 26,208	26,392
Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	8 years
Property and equipment, at cost	$ 12,437	10,518
Building and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	30 years
Property and equipment, at cost	$ 14,188	12,346
Building and Leasehold Improvements [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	31 years
Property and equipment, at cost	$ 8,877	8,124
Furniture, Fixtures and Equipment [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Weighted-Average Original Useful Life	11 years
Property and equipment, at cost	$ 5,501	4,843
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	2,991	1,752
Construction in Process [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	2,676	1,506
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	1,539	1,332
Land [Member] | NBCUniversal Media LLC [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 1,129	$ 1,039