Acquisitions, Dispositions And Other Adjustments (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Acquisition and Dispositions [Line Items]
Acquisition of business - purchase price (in millions)		$ 117	$ 234
Time Warner Inc. [Member]
Acquisition and Dispositions [Line Items]
Acquisition of business - acquisition period				Jun. 14, 2018
Time Warner Inc. [Member] | WarnerMedia [Member]
Acquisition and Dispositions [Line Items]
Acquisition of business - purchase price (in millions)	$ 79,358
Time Warner Inc. [Member] | WarnerMedia [Member] | Cash [Member]
Acquisition and Dispositions [Line Items]
Acquisition of business - purchase price (in millions)	42,100
Time Warner Inc. [Member] | WarnerMedia [Member] | Common Stock [Member]
Acquisition and Dispositions [Line Items]
Acquisition of business - purchase price (in millions)	$ 36,599