v3.26.1
Employee Benefit Plan, Master Trust (Interest in Investment Fund) (Details) - USD ($)
$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
EBP-43-1301883-021 [Group Trust]    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value $ 7,170,886 $ 6,862,851
EBP, Net Asset Available for Benefit 11,301,767 11,321,338
EBP-43-1301883-021 [Group Trust] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 816,124 843,105
EBP-43-1301883-021 [Group Trust] | Corporate debt    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 874,643 939,989
EBP-43-1301883-021 [Group Trust] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 505,762 319,763
EBP-43-1301883-021 [Group Trust] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 3,807,953 3,962,205
EBP-43-1301883-021 [Group Trust] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 989,007 589,466
EBP-43-1301883-021 [Group Trust] | Mutual funds    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 174,429 202,817
EBP-43-1301883-021 [Group Trust] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 23  
EBP, Other Liability (Asset) at Fair Value   (2,534)
EBP-43-1301883-021 [Group Trust] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 4,561,487 4,879,047
EBP, Other Liability (Asset) at Fair Value (430,606) (420,560)
EBP-43-1301883-022 [Master Trust]    
EBP, Master Trust [Line Items]    
Assets at fair value 45,305,719 42,649,973
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 34,518,159 31,848,071
EBP, Net Asset Available for Benefit 45,304,545 42,648,278
EBP-43-1301883-022 [Master Trust] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 42  
EBP-43-1301883-022 [Master Trust] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 26,715,343 24,697,041
EBP-43-1301883-022 [Master Trust] | Mutual funds    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 42,365 48,445
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 2,620,014 2,470,068
Investment, Plan Interest in Master Trust, Fair Value 3,047,692 2,888,795
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 793,952 822,920
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 850,881 916,579
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 492,022 312,107
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 887,253 815,461
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 21,134 16,868
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   (2,473)
Investment, Plan Interest in Master Trust, Fair Value 22  
AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 0 0
EBP, Other Liability (Asset) at Fair Value (427,678) 418,727
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 73,167 60,587
Investment, Plan Interest in Master Trust, Fair Value 85,110 70,858
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 22,172 20,185
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 23,762 22,482
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 13,740 7,656
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 24,777 20,002
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 590 414
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   (61)
Investment, Plan Interest in Master Trust, Fair Value 1  
AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 0 0
EBP, Other Liability (Asset) at Fair Value (11,943) 10,271
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 3,328,355 3,247,966
Investment, Plan Interest in Master Trust, Fair Value 3,328,213 3,248,098
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 2,441,849 2,756,137
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 851,739 466,275
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 34,622 25,683
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   0
Investment, Plan Interest in Master Trust, Fair Value 0  
AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 0 0
EBP, Other Liability (Asset) at Fair Value 142 132
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 37,867 30,488
Investment, Plan Interest in Master Trust, Fair Value 37,865 30,489
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 27,781 25,871
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 9,690 4,377
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 394 241
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   0
Investment, Plan Interest in Master Trust, Fair Value 0  
AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 0 0
EBP, Other Liability (Asset) at Fair Value 2 1
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 539,929 457,631
Investment, Plan Interest in Master Trust, Fair Value 539,031 457,055
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 903
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 413,231 335,590
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 123,671 115,662
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 1,698 4,391
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   0
Investment, Plan Interest in Master Trust, Fair Value 0  
AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 0 0
EBP, Other Liability (Asset) at Fair Value 898 (576)
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 17,066 12,472
Investment, Plan Interest in Master Trust, Fair Value 17,038 12,456
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 25
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 13,062 9,144
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 3,907 3,152
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 54 120
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   0
Investment, Plan Interest in Master Trust, Fair Value 0  
AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 0 0
EBP, Other Liability (Asset) at Fair Value 28 (16)
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 4,299,262 4,626,235
Investment, Plan Interest in Master Trust, Fair Value 106,383 142,307
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 106,383 142,307
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   0
Investment, Plan Interest in Master Trust, Fair Value 0  
AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 4,185,589 4,476,607
EBP, Other Liability (Asset) at Fair Value 7,290 (7,321)
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP]    
EBP, Master Trust [Line Items]    
EBP, Net Asset Available for Benefit 386,107 415,891
Investment, Plan Interest in Master Trust, Fair Value 9,554 12,793
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Mortgage-backed securities    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Corporate debt    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | US Treasury and Government [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Common/collective trust funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Equity Securities [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Mutual funds    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 9,554 12,793
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Derivative [Member]    
EBP, Master Trust [Line Items]    
EBP, Other Liability (Asset) at Fair Value   0
Investment, Plan Interest in Master Trust, Fair Value 0  
AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | EBP, Other Investment [Member]    
EBP, Master Trust [Line Items]    
Assets at contract value 375,898 402,440
EBP, Other Liability (Asset) at Fair Value 655 (658)
Non-US [Member] | EBP-43-1301883-021 [Group Trust] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 2,945 8,040
Non-US [Member] | AT&T Total Return Bond Fund | EBP-43-1301883-022 [Master Trust] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 2,428 7,333
Non-US [Member] | AT&T Total Return Bond Fund | EBP-58-1533433-004 [BSSP] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 68 180
Non-US [Member] | AT&T U.S. Stock Fund | EBP-43-1301883-022 [Master Trust] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 3 3
Non-US [Member] | AT&T U.S. Stock Fund | EBP-58-1533433-004 [BSSP] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
Non-US [Member] | AT&T International Stock Fund | EBP-43-1301883-022 [Master Trust] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 431 509
Non-US [Member] | AT&T International Stock Fund | EBP-58-1533433-004 [BSSP] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 15 15
Non-US [Member] | AT&T Stable Value Fund | EBP-43-1301883-022 [Master Trust] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value 0 0
Non-US [Member] | AT&T Stable Value Fund | EBP-58-1533433-004 [BSSP] | Cash and Cash Equivalents [Member]    
EBP, Master Trust [Line Items]    
Investment, Plan Interest in Master Trust, Fair Value $ 0 $ 0