Number of persons employed by the Entity

No definition available.

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- Definition

Contract year relevant to concentration of labor risk discussion.

+ References

No definition available.

+ Details

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- Definition

Number of employees under contracts where union may call a work stoppage

+ References

No definition available.

+ Details

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- Definition

For an entity that discloses a concentration risk as a percentage of some financial balance or benchmark, this item identifies a second characteristic of the concentration. For example, "Europe" is the second characteristic in the phrase: "net assets in Europe are 70% of total net assets".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

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-Paragraph 21
-Subparagraph (a)
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 310
-Section 50
-Paragraph 2
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

+ Details

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Balance Type:	na
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- Definition

Description of any concentration of labor subject to collective bargaining agreements, including the general nature of the risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-Section 50
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6327-108592

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

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Data Type:	num:percentItemType
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Period Type:	duration

- Details

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- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	t_LaborContractCoverageAxis=t_MidwestWirelineMember
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Data Type:	na
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Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
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Data Type:	na
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- Details

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Additional Financial Information (Narrative) (Details)	12 Months Ended
Additional Financial Information (Narrative) (Details)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2018
Concentration Risk [Line Items]
Number of customers exceeding threshold for significance	0	0	0
Workforce Subject to Collective Bargaining Arrangements [Member]
Concentration Risk [Line Items]
Approximate number of persons employed at a point in time				252,000
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Concentration Risk [Line Items]
Percentage of employees represented by CWA, IBEW, or other unions	46%
Number of employees under contracts where union may call a work stoppage	23,000
Relevant union contract expiration year	2018
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] \| Southeast Region [Member]
Concentration Risk [Line Items]
Number of employees under contracts where union may call a work stoppage	10,000
Relevant union contract expiration year	2018
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] \| Midwest Wireline [Member]
Concentration Risk [Line Items]
Number of employees under contracts where union may call a work stoppage	10,000
Relevant union contract expiration year	2018
Sales Revenue, Net [Member]
Concentration Risk [Line Items]
Threshold for customer significance (as a percent of consolidated revenues) (in hundredths)	0.00%	0.00%	0.00%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Threshold for customer significance (as a percent of consolidated revenues) (in hundredths)	10.00%	10.00%	10.00%