v3.19.3.a.u2
Segment Information (Reconciliation of Operating Profit (Loss) from Segments to Consolidated) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2019
 [1],[2]
Sep. 30, 2019
 [1]
Jun. 30, 2019
 [1]
Mar. 31, 2019
 [1]
Dec. 31, 2018
 [1]
Sep. 30, 2018
 [1]
Jun. 30, 2018
 [1]
Mar. 31, 2018
 [1]
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income $ 5,321 $ 7,901 $ 7,500 $ 7,233 $ 6,160 $ 7,269 $ 6,466 $ 6,201 $ 7,269 $ 6,466 $ 6,201 $ 27,955 $ 26,096 $ 19,970
Interest expense                       8,422 7,957 6,300
Equity in net income (loss) of affiliates                       6 (48) (128)
Other income (expense) - net                       (1,071) 6,782 1,597
Income Before Income Taxes                       18,468 24,873 15,139
Operating Segments [Member]                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       42,050 38,367 32,428
Equity in net income (loss) of affiliates                       (189) (59) (58)
Income Before Income Taxes                       42,239 38,426 32,486
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                       32,230 32,108 31,488
Equity in net income (loss) of affiliates                       0 0 0
Income Before Income Taxes                       32,230 32,108 31,488
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                       9,164 5,670 91
Equity in net income (loss) of affiliates                       (162) (25) 29
Income Before Income Taxes                       9,326 5,695 62
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                       (662) (744) (353)
Equity in net income (loss) of affiliates                       (27) (34) (87)
Income Before Income Taxes                       (635) (710) (266)
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                       1,318 1,333 1,202
Equity in net income (loss) of affiliates                       0 0 0
Income Before Income Taxes                       1,318 1,333 1,202
Certain Significant Items [Member]                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (2,125) (925) (4,156)
Certain Significant 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                       (1,962) (1,730) (1,682)
Merger and intergration charges                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (1,032) (1,234) (798)
Amortization of intangibles acquired                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (7,460) (6,931) (4,608)
Abandonments and impairments                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (1,458) (46) (2,914)
Employee separation charges                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (624) (587) (445)
Other noncash charges (credits) [Member]                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (43) (111) 49
Natural disaster items                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       0 (181) (626)
Tax Reform Special Bonus [Member]                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       0 0 (220)
Segment equity in net income of affiliates                            
Segment Reporting Reconciling Item For Operating Income (Loss) From Segment To Consolidated Statements Of Income [Line Items]                            
AT&T Operating Income                       (189) (59) (58)
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                       $ (1,516) $ (1,451) $ (1,214)
[1] Includes actuarial gains and losses on pension and postretirement benefit plans (Note 15).
[2] Includes an asset abandonment charge (Note 7).