The number of debt exchange offers completed within the stated period.

No definition available.

Name:	t_DebtInstrumentExchangeOffersCompleted
Namespace Prefix:	t_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of debt instruments issued in a particular group of notes.

+ References

No definition available.

+ Details

Name:	t_DebtInstrumentNumberOfDebtInstrumentsIssued
Namespace Prefix:	t_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The stated amount payable to holders if debt instrument is held to maturity debt security.

+ References

No definition available.

+ Details

Name:	t_DebtInstrumentRedemptionAmount
Namespace Prefix:	t_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average date of a group of debt instruments scheduled for full repayment, in 'PnYnMnDTnHnMnS' format.

+ References

No definition available.

+ Details

Name:	t_DebtInstrumentWeightedAverageMaturityPeriod
Namespace Prefix:	t_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

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

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

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

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for cost incurred in the modification of term of existing debt agreement in order for the entity to achieve some advantage.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfDebtRestructuringCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

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

- Details

Name:	us-gaap_TransactionTypeAxis=t_DebtExchangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_NotesAndDebenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_NewDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_GlobalNotesDueBetween2020And2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TransactionTypeAxis=t_FirstDebtExchangeOfferMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_GlobalNotesDueBetween2022And2097Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TransactionTypeAxis=t_SecondDebtExchangeOfferMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_AttIncGlobalNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_SeriesOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=t_SeriesTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Financing Activities) (Narrative) (Details) $ in Millions		12 Months Ended
	Dec. 02, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 01, 2017 USD ($)
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		$ 48,793	$ 10,140	$ 33,969
Debt Exchange [Member]
Debt Instrument [Line Items]
Debt Instrument - Exchange Offers Completed	2
Notes And Debentures [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Interest Rate		4.40%	4.20%
Debt Instrument, Redemption Amount		$ 12,339
Notes And Debentures [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate		1.40%
Notes And Debentures [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate		5.79%
New Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Maturity Period		18 years
Debt Instrument Weighted Average Interest Rate		4.35%
Debt instrument - principal amount		$ 49,161
Global Notes Due Between 2020 and 2023 [Member] \| First Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Early redemption of long-term debt	$ 5,448
Global Notes Due Between 2020 and 2023 [Member] \| Minimum [Member] \| First Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					0.00%
Global Notes Due Between 2020 and 2023 [Member] \| Maximum [Member] \| First Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					5.20%
Global Notes Due Between 2022 and 2097 [Member] \| Second Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Early redemption of long-term debt	$ 3,726
Global Notes Due Between 2022 and 2097 [Member] \| Minimum [Member] \| Second Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					5.85%
Global Notes Due Between 2022 and 2097 [Member] \| Maximum [Member] \| Second Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					8.75%
AT&T Inc. Global Notes [Member] \| First Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt Instrument - Number Of Debt Instruments Issued	2
AT&T Inc. Global Notes [Member] \| Second Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instrument - principal amount					$ 3,736
Payments of Debt Restructuring Costs	$ 449
AT&T Inc. Global Notes [Member] \| Minimum [Member] \| Second Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					5.15%
AT&T Inc. Global Notes [Member] \| Maximum [Member] \| Second Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					8.75%
Series One [Member] \| First Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instrument - principal amount					$ 5,605
Debt instument - stated percentage rate					4.10%
Series Two [Member] \| First Debt Exchange Offer [Member]
Debt Instrument [Line Items]
Debt instument - stated percentage rate					4.30%