Goodwill And Other Intangible Assets (Summary Of Changes In Carrying Amount Of Goodwill, By Segment) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 146,370	$ 105,449
Reallocation		0
Acquisition	66	41,678
Dispositions, currency exchange and other	(195)	(757)
Ending balance	146,241	146,370
Business Solutions [Member]
Goodwill [Roll Forward]
Beginning balance	0	45,395
Reallocation		(45,395)
Acquisition	0	0
Dispositions, currency exchange and other	0	0
Ending balance	0	0
Consumer Mobility [Member]
Goodwill [Roll Forward]
Beginning balance	0	16,540
Reallocation		(16,540)
Acquisition	0	0
Dispositions, currency exchange and other	0	0
Ending balance	0	0
Communications [Member]
Goodwill [Roll Forward]
Beginning balance	100,551	39,280
Reallocation		61,075
Acquisition	0	422
Dispositions, currency exchange and other	(317)	(226)
Ending balance	100,234	100,551
WarnerMedia [Member]
Goodwill [Roll Forward]
Beginning balance	40,698	0
Reallocation		681
Acquisition	0	40,036
Dispositions, currency exchange and other	181	(19)
Ending balance	40,879	40,698
Latin America Business Segment [Member]
Goodwill [Roll Forward]
Beginning balance	3,718	4,234
Reallocation		(32)
Acquisition	0	0
Dispositions, currency exchange and other	(56)	(484)
Ending balance	3,662	3,718
Xandr [Member]
Goodwill [Roll Forward]
Beginning balance	1,403	0
Reallocation		211
Acquisition	66	1,220
Dispositions, currency exchange and other	(3)	(28)
Ending balance	$ 1,466	$ 1,403

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease), classified as other, of an asset representing the future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillOtherIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_GoodwillRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of transfers into (out of) an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillTransfers
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_SubsegmentsAxis=t_BusinessSolutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=t_ConsumerMobilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=t_CommunicationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=t_WarnerMediaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=t_LatinAmericaBusinessSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=t_XandrMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: