| Disclosure of Reclassification Amount [Text Block] |
8. RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (AOCI)
Reclassification adjustments and other activity impacting accumulated other comprehensive income (loss) during the three and six months ended June 30, 2025 and June 30, 2024 are as follows (in millions):
| | | | | | | | | | | | | | | | | | | | | | | | | | | Defined Benefit Plans | | Foreign Currency Translation Adjustments | | Unrecognized Gain (Loss) on Hedges | | Total | | Balance at March 31, 2025 | $ | (157.5) | | | $ | (163.7) | | | $ | (5.8) | | | $ | (327.0) | | | | | | | | | | | | Other comprehensive income (loss) before reclassifications | — | | | 24.8 | | | (6.9) | | | 17.9 | | | | | | | | | | | | Income tax effect of other comprehensive income (loss) before reclassifications | — | | | — | | | 1.4 | | | 1.4 | | | | | | | | | | | | Amounts reclassified from accumulated other comprehensive income (loss) | (0.3) | | (a) | — | | | 18.5 | | (b) | 18.2 | | | | | | | | | | | | Income taxes reclassified into net income | 0.1 | | | — | | | (4.2) | | | (4.1) | | | | | | | | | | | | Net change in accumulated other comprehensive income (loss) | (0.2) | | | 24.8 | | | 8.8 | | | 33.4 | | | | | | | | | | | | Balance at June 30, 2025 | $ | (157.7) | | | $ | (138.9) | | | $ | 3.0 | | | $ | (293.6) | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | Defined Benefit Plans | | Foreign Currency Translation Adjustments | | Unrecognized Gain (Loss) on Hedges | | Total | | Balance at March 31, 2024 | $ | (145.9) | | | $ | (157.6) | | | $ | 35.5 | | | $ | (268.0) | | | | | | | | | | | | Other comprehensive loss before reclassifications | — | | | (14.3) | | | (12.8) | | | (27.1) | | | | | | | | | | | | Income tax effect of other comprehensive loss before reclassifications | — | | | — | | | 2.6 | | | 2.6 | | | | | | | | | | | | Amounts reclassified from accumulated other comprehensive income (loss) | (0.9) | | (a) | — | | | (8.8) | | (b) | (9.7) | | | | | | | | | | | | Income taxes reclassified into net income | 0.3 | | | — | | | — | | | 0.3 | | | | | | | | | | | | Net change in accumulated other comprehensive income (loss) | (0.6) | | | (14.3) | | | (19.0) | | | (33.9) | | | | | | | | | | | | Balance at June 30, 2024 | $ | (146.5) | | | $ | (171.9) | | | $ | 16.5 | | | $ | (301.9) | |
| | | | | | | (a) | These amounts were reclassified from AOCI to Other income (expense), net for the three months ended June 30, 2025 and June 30, 2024. | | | | (b) | The amounts reclassified from AOCI included $1.9 million in cost of goods sold (COGS), $(0.4) million in interest expense and $17.0 million in Other income (expense), net for the three months ended June 30, 2025 and $(5.7) million in COGS, $(1.1) million in interest expense and $(2.0) million in Other income (expense), net for the three months ended June 30, 2024. |
| | | | | | | | | | | | | | | | | | | | | | | | | | | Defined Benefit Plans | | Foreign Currency Translation Adjustments | | Unrecognized Gain (Loss) on Hedges | | Total | | Balance at December 31, 2024 | $ | (157.2) | | | $ | (187.0) | | | $ | (8.0) | | | $ | (352.2) | | | | | | | | | | | | Other comprehensive income (loss) before reclassifications | — | | | 41.7 | | | (14.9) | | | 26.8 | | | | | | | | | | | | Income tax effect of other comprehensive income (loss) before reclassifications | — | | | — | | | 3.1 | | | 3.1 | | | | | | | | | | | | Amounts reclassified from accumulated other comprehensive income (loss) | (0.7) | | (a) | 6.4 | | (c) | 29.6 | | (b) | 35.3 | | | | | | | | | | | | Income taxes reclassified into net income | 0.2 | | | — | | | (6.8) | | | (6.6) | | | | | | | | | | | | Net change in accumulated other comprehensive income (loss) | (0.5) | | | 48.1 | | | 11.0 | | | 58.6 | | | | | | | | | | | | Balance at June 30, 2025 | $ | (157.7) | | | $ | (138.9) | | | $ | 3.0 | | | $ | (293.6) | |
| | | | | | | | | | | | | | | | | | | | | | | | | Defined Benefit Plans | | Foreign Currency Translation Adjustments | | Unrecognized Gain (Loss) on Hedges | | Total | Balance at December 31, 2023 | $ | (145.3) | | | $ | (142.3) | | | $ | 24.7 | | | $ | (262.9) | | | | | | | | | | | Other comprehensive income (loss) before reclassifications | — | | | (29.6) | | | 11.0 | | | (18.6) | | | | | | | | | | | Income tax effect of other comprehensive income (loss) before reclassifications | — | | | — | | | (2.4) | | | (2.4) | | | | | | | | | | | Amounts reclassified from accumulated other comprehensive income (loss) | (1.8) | | (a) | — | | | (18.8) | | (b) | (20.6) | | | | | | | | | | | Income taxes reclassified into net income | 0.6 | | | — | | | 2.0 | | | 2.6 | | | | | | | | | | | Net change in accumulated other comprehensive income (loss) | (1.2) | | | (29.6) | | | (8.2) | | | (39.0) | | | | | | | | | | Balance at June 30, 2024 | $ | (146.5) | | | $ | (171.9) | | | $ | 16.5 | | | $ | (301.9) | |
| | | | | | | (a) | These amounts were reclassified from AOCI to Other income (expense), net for the six months ended June 30, 2025 and June 30, 2024. | | | | (b) | The amounts reclassified from AOCI included $6.0 million in COGS, $(1.4) million in interest expense and $25.0 million in Other income (expense), net for the six months ended June 30, 2025 and $(10.4) million in COGS, $(1.4) million in interest expense and $(7.0) million in Other income (expense), net for the six months ended June 30, 2024. | | (c) | The amount reclassified from AOCI to net income for the six months ended June 30, 2025 reflects AAM's 50% share of the cumulative translation adjustment associated with the two Chinese joint ventures that we exited in the first quarter of 2025. This amount was reclassified to Other income (expense), net. See Note 2 - Acquisitions and Dispositions for further details. |
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