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Segment Information - Narrative (Details) $ in Millions |  | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jan. 01, 2020 USD ($) | Sep. 30, 2021 USD ($) segment | Sep. 30, 2020 | Dec. 31, 2020 USD ($) | Mar. 31, 2020 | Dec. 31, 2019
Segment Reporting Information [Line Items] |  |  |  |  |  |
Number of reportable segments | segment |  | 4 |  |  |  |
Goodwill |  | $ 4,077 |  | $ 4,102 |  |
Goodwill, impairment loss | $ 0 |  |  |  |  |
Revenue Benchmark | Customer Concentration Risk | Aerospace |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  | 60.00% | 70.00% |  |  |
Revenue Benchmark | Customer Concentration Risk | Aerospace | General Electric Company | Engine Products |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Concentration risk, percentage |  | 13.00% | 11.00% |  |  |
Engineered Structures |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Goodwill reallocated, increase (decrease) | 17 |  |  |  |  |
Percentage of fair value in excess of carrying amount |  |  |  |  | 15.00% | 60.00%
Engine Products |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Goodwill reallocated, increase (decrease) | $ (17) |  |  |  |  |

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