Revenue (Revenue by Geographic Location) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 26,858	$ 21,735	$ 53,717	$ 44,526
United States [Member]
Disaggregation of Revenue [Line Items]
Revenue	20,539	19,931	40,996	40,816
Europe [Member]
Disaggregation of Revenue [Line Items]
Revenue	5,297	699	10,667	1,520
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,022	1,105	2,054	2,190
NBCUniversal Media LLC [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,227	8,313	16,572	17,843
NBCUniversal Media LLC [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Revenue	6,669	6,533	13,292	14,187
NBCUniversal Media LLC [Member] | Foreign [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 1,558	$ 1,780	$ 3,280	$ 3,656