v3.20.4

Other Comprehensive Income (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Other comprehensive income (loss) before reclassifications | $ 647 | $ 2,635 | $ (801)
Amounts reclassified from accumulated OCI | (1,787) | (1,414) | (1,309)
Other comprehensive income (loss) attributable to AT&T | (1,140) | 1,221 | (2,110)
Accumulated Other Comprehensive Income |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance | 5,470 | 4,249 | 7,017
Other comprehensive income (loss) attributable to AT&T | (1,140) | 1,221 | (2,110)
Accumulated other comprehensive income, ending balance | 4,330 | 5,470 | 4,249
Accumulated Other Comprehensive Income | Amounts reclassified to retained earnings |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance |  |  | (658)
Foreign Currency Translation Adjustment |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance | (3,056) | (3,084) | (2,054)
Other comprehensive income (loss) before reclassifications | (870) | 28 | (1,030)
Amounts reclassified from accumulated OCI | 0 | 0 | 0
Other comprehensive income (loss) attributable to AT&T | (870) | 28 | (1,030)
Accumulated other comprehensive income, ending balance | (3,926) | (3,056) | (3,084)
Foreign Currency Translation Adjustment | Amounts reclassified to retained earnings |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance |  |  | 0
Net Unrealized Gains (Losses) on Available-for-Sale Securities |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance | 48 | (2) | 660
Other comprehensive income (loss) before reclassifications | 78 | 50 | (4)
Amounts reclassified from accumulated OCI | (15) | 0 | 0
Other comprehensive income (loss) attributable to AT&T | 63 | 50 | (4)
Accumulated other comprehensive income, ending balance | 111 | 48 | (2)
Net Unrealized Gains (Losses) on Available-for-Sale Securities | Amounts reclassified to retained earnings |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance |  |  | (658)
Net Unrealized Gains (Losses) on Cash Flow Hedges |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance |  |  | 1,402
Other comprehensive income (loss) before reclassifications |  |  | (597)
Amounts reclassified from accumulated OCI |  |  | 13
Other comprehensive income (loss) attributable to AT&T |  |  | (584)
Net Unrealized Gains (Losses) on Cash Flow Hedges | Amounts reclassified to retained earnings |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance |  |  | 0
Net Unrealized Gains (Losses) on Cash Flow Hedges |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance | (37) | 818 |
Other comprehensive income (loss) before reclassifications | (811) | (900) |
Amounts reclassified from accumulated OCI | 69 | 45 |
Other comprehensive income (loss) attributable to AT&T | (742) | (855) |
Accumulated other comprehensive income, ending balance | (779) | (37) | 818
Defined Benefit Postretirement Plans |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance | 8,515 | 6,517 | 7,009
Other comprehensive income (loss) before reclassifications | 2,250 | 3,457 | 830
Amounts reclassified from accumulated OCI | (1,841) | (1,459) | (1,322)
Other comprehensive income (loss) attributable to AT&T | 409 | 1,998 | (492)
Accumulated other comprehensive income, ending balance | $ 8,924 | $ 8,515 | 6,517
Defined Benefit Postretirement Plans | Amounts reclassified to retained earnings |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Accumulated other comprehensive income, beginning balance |  |  | $ 0

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