Employee Benefit Plan, Master Trust (AT&T Master Trust Assets at Fair Value) (Details) - EBP-43-1301883-022 [Master Trust] $ in Thousands	Dec. 31, 2025 USD ($)
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	$ 34,518,159
Fair Value, Inputs, Level 1, Level 2, and Level 3
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	7,802,816
Fair Value, Inputs, Level 1
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	7,768,827
Fair Value, Inputs, Level 2
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	33,989
Fair Value, Inputs, Level 3
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	0
Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 1, Level 2, and Level 3
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	42
AT&T common stock \| Fair Value, Inputs, Level 1, Level 2, and Level 3
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	4,023,865
Mutual funds \| Fair Value, Inputs, Level 1, Level 2, and Level 3
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	42,365
Self-directed brokerage accounts \| Fair Value, Inputs, Level 1, Level 2, and Level 3
EBP, Investment, Fair Value and NAV [Line Items]
EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value	$ 3,736,544