Segment Information (Reconciliation Of Operating Income Loss to Consolidated Statement Of Income) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	$ 7,269	$ 5,807	$ 19,936	$ 18,689
Interest expense	(2,051)	(1,686)	(5,845)	(4,374)
Equity in net income (loss) of affiliates	(64)	11	(71)	(148)
Other income (expense) - net	1,053	842	5,108	2,255
Income Before Income Taxes	6,207	4,974	19,128	16,422
Operating Segments [Member] \| Communications [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	8,183	8,071	24,626	24,821
Equity in net income (loss) of affiliates	(1)	0	(3)	0
Income Before Income Taxes	8,182	8,071	24,623	24,821
Operating Segments [Member] \| WarnerMedia [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	2,567	8	3,047	44
Equity in net income (loss) of affiliates	(39)	(6)	(55)	(23)
Income Before Income Taxes	2,528	2	2,992	21
Operating Segments [Member] \| Latin America [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	(210)	(142)	(486)	(319)
Equity in net income (loss) of affiliates	9	17	24	62
Income Before Income Taxes	(201)	(125)	(462)	(257)
Operating Segments [Member] \| Xandr [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	333	294	952	873
Equity in net income (loss) of affiliates	0	0	0	0
Income Before Income Taxes	333	294	952	873
Operating Segments [Member] \| Segment Contribution [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	10,873	8,231	28,139	25,419
Equity in net income (loss) of affiliates	(31)	11	(34)	39
Income Before Income Taxes	10,842	8,242	28,105	25,458
Segment Reconciling Items [Member] \| Corporate and Other [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	(471)	(443)	(1,355)	(1,331)
Segment Reconciling Items [Member] \| Merger and intergration items [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	(362)	(134)	(750)	(622)
Segment Reconciling Items [Member] \| Amortization of intangibles acquired [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	(2,329)	(1,136)	(4,669)	(3,508)
Segment Reconciling Items [Member] \| Employee separate charges [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	(75)	(208)	(259)	(268)
Segment Reconciling Items [Member] \| Gain on wireless spectrum transactions [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	0	0	0	181
Segment Reconciling Items [Member] \| Natural Disaster Charges [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	0	(207)	(104)	(207)
Segment Reconciling Items [Member] \| Foreign Currency Devaluation [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	0	0	(44)	(98)
Segment Reconciling Items [Member] \| Segment equity in net (income) loss of affiliates
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	31	(11)	34	(39)
Segment Reconciling Items [Member] \| Eliminations and consolidations [Member]
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]
AT&T Operating Income	$ (367)	$ (296)	$ (1,022)	$ (877)

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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