v3.26.1
Employee Benefit Plan, Master Trust (Financial Position of Master Trust) (Details) - USD ($)
$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
EBP-43-1301883-022 [Master Trust]    
Net Asset Available for Benefit [Abstract]    
Net other assets and liabilities $ (1,174) $ (1,695)
EBP, Net Asset Available for Benefit 45,304,545 42,648,278
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-43-1301883-022 [Master Trust] | Cash and Cash Equivalents [Member]    
Net Asset Available for Benefit [Abstract]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 42  
EBP-43-1301883-022 [Master Trust] | AT&T common stock    
Net Asset Available for Benefit [Abstract]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 4,023,865 3,859,277
EBP-43-1301883-022 [Master Trust] | Mutual funds    
Net Asset Available for Benefit [Abstract]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 42,365 48,445
EBP-43-1301883-022 [Master Trust] | Common/collective trust funds    
Net Asset Available for Benefit [Abstract]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 26,715,343 24,697,041
EBP-43-1301883-022 [Master Trust] | Fidelity BrokerageLink®    
Net Asset Available for Benefit [Abstract]    
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value 3,736,544 3,243,308
EBP-43-1301883-022 [Master Trust] | Investment in Group Trust    
Net Asset Available for Benefit [Abstract]    
Investment, Plan Interest in Master Trust, Fair Value 10,787,560 10,801,902
EBP-43-1301883-009 [ARSP]    
Net Asset Available for Benefit [Abstract]    
Net other assets and liabilities (863) (1,418)
EBP, Net Asset Available for Benefit 45,745,042 43,121,795
Investment, Plan Interest in Master Trust, Fair Value 45,195,392 42,549,062
Assets at fair value 45,196,255 42,550,480
EBP-43-1301883-009 [ARSP] | Cash and Cash Equivalents [Member]    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 42  
EBP-43-1301883-009 [ARSP] | AT&T common stock    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 4,017,982 3,853,789
EBP-43-1301883-009 [ARSP] | Mutual funds    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 42,201 48,290
EBP-43-1301883-009 [ARSP] | Common/collective trust funds    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 26,645,834 24,633,665
EBP-43-1301883-009 [ARSP] | Fidelity BrokerageLink®    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 3,736,234 3,243,039
EBP-43-1301883-009 [ARSP] | Investment in Group Trust    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 10,753,962 10,771,697
EBP-43-1301883-011 [PRRSP]    
Net Asset Available for Benefit [Abstract]    
Net other assets and liabilities (311) (277)
EBP, Net Asset Available for Benefit 109,758 99,901
Investment, Plan Interest in Master Trust, Fair Value 109,153 99,216
Assets at fair value 109,464 99,493
EBP-43-1301883-011 [PRRSP] | Cash and Cash Equivalents [Member]    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 0  
EBP-43-1301883-011 [PRRSP] | AT&T common stock    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 5,883 5,488
EBP-43-1301883-011 [PRRSP] | Mutual funds    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 164 155
EBP-43-1301883-011 [PRRSP] | Common/collective trust funds    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 69,509 63,376
EBP-43-1301883-011 [PRRSP] | Fidelity BrokerageLink®    
Net Asset Available for Benefit [Abstract]    
Assets at fair value 310 269
EBP-43-1301883-011 [PRRSP] | Investment in Group Trust    
Net Asset Available for Benefit [Abstract]    
Assets at fair value $ 33,598 $ 30,205