Investments (Schedule of Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Equity method	$ 4,035	$ 3,546
Marketable equity securities	341	433
Nonmarketable equity securities	1,805	1,186
Other investments	1,796	1,785
Total investments	7,977	6,950
Less: Current investments	94	19
Long-term Investments	7,883	6,931
NBCUniversal Media LLC [Member]
Schedule of Investments [Line Items]
Equity method	707	690
Marketable equity securities	162	430
Nonmarketable equity securities	811	696
Total investments	1,680	1,816
Long-term Investments	$ 1,680	$ 1,816