Revenue (Revenue by Geographic Location) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 28,398	$ 26,827	$ 26,858	$ 26,859	$ 27,846	$ 22,135	$ 21,735	$ 22,791	$ 108,942	$ 94,507	$ 85,029
United States [Member]
Disaggregation of Revenue [Line Items]
Revenue									82,952	82,233	77,246
Europe [Member]
Disaggregation of Revenue [Line Items]
Revenue									21,553	7,721	3,190
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue									4,437	4,553	4,593
NBCUniversal Media LLC [Member]
Disaggregation of Revenue [Line Items]
Revenue									34,021	35,895	32,950
NBCUniversal Media LLC [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Revenue									27,002	28,309	25,303
NBCUniversal Media LLC [Member] | Foreign [Member]
Disaggregation of Revenue [Line Items]
Revenue									$ 7,019	$ 7,586	$ 7,647