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Preparation Of Interim Financial Statements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Operating lease liability	$ 21,325
Operating Lease, Right-of-Use Asset	20,235	$ 0
Retained earnings	59,424	58,753
Other current assets	$ 14,575	$ 17,704
Mexico [Member] \| Spectrum Licenses [Member]
Change in Accounting Estimate [Line Items]
Estimated economic useful life	25 years
Time Warner Inc. [Member]
Acquisition and Dispositions [Line Items]
Acquisition of business - acquisition period		Jun. 14, 2018
ASU 2016-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Operating lease liability			$ 22,121
Operating Lease, Right-of-Use Asset			22,121
Net Assets			20,960
Retained earnings			316
Transition Option Elected [Prospective/Retrospective/Modified Prospective/Modified Retrospective]	Modified Retrospective
ASU Adoption Date [CCYY-MM-DD format]	Jan. 01, 2019
ASU Early Adoption [true/false]	false
Prior Period Not Restated [true/false]	true
Significant effect on the financial statements [Yes/No]	No
ASU 2019-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Transition Option Elected [Prospective/Retrospective/Modified Prospective/Modified Retrospective]	Prospective
ASU Adoption Date [CCYY-MM-DD format]	Jan. 01, 2019
ASU Early Adoption [true/false]	true
Prior Period Not Restated [true/false]	true
Significant effect on the financial statements [Yes/No]	No
ASU 2019-02 [Member] \| Programming Inventory Costs [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Other current assets			(2,274)
Other Assets			$ 2,274