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Acquisitions, Dispositions And Other Adjustments (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended			9 Months Ended		12 Months Ended
	Jun. 30, 2019	Apr. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Acquisition and Dispositions [Line Items]
Acquisition of business - purchase price (in millions)				$ 1,124	$ 43,116
Cash proceeds from sale of businesses and interest in affiliates				$ 3,775	$ 983
Common Stock [Member] \| Hudson Yards North Tower Holding LLC [Member] \| Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Acquisition and Dispositions [Line Items]
Disposal Date	Jun. 01, 2019
Cash proceeds from sale of businesses and interest in affiliates	$ 2,081
Gain (Loss) on sale of investment	$ (100)
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
Hulu [Member] \| Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Acquisition and Dispositions [Line Items]
Disposal Date		Apr. 01, 2019
Cash proceeds from sale of businesses and interest in affiliates		$ 1,430
Gain (Loss) on sale of investment		$ 740