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Segment Information - Narrative (Details) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Sep. 30, 2019 segment | Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items] |  |  |  |  |
Number of operating and reportable segments | segment |  |  |  | 2 |
Amount related to settlements of certain customer claims |  |  |  |  | $ 38
Engineered Products and Forgings |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Long lived asset impairment charge |  | $ 428 |  |  |
AWTP |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Goodwill, amount reallocated due to restructuring | $ 7 |  |  |  |
BCS |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Goodwill, amount reallocated due to restructuring | 68 |  |  |  |
Arconic Engines |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Goodwill, amount reallocated due to restructuring |  | 105 |  |  |
Long lived asset impairment charge | $ 428 |  |  |  |
Aluminum Extrusions |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Goodwill, amount reallocated due to restructuring |  |  | $ 110 |  |
Arconic Engineered Structures |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Goodwill, amount reallocated due to restructuring |  | $ (105) | $ (110) |  |

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