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Goodwill and Other Intangible Assets - Goodwill (Details) - USD ($) |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jul. 12, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Jun. 03, 2019 | Dec. 31, 2016
Goodwill [Line Items] |  |  |  |  |  |
Goodwill |  | $ 525,800,000 | $ 534,700,000 |  |  |
Period increase (decrease) in goodwill |  | (8,900,000) |  |  |  |
Impairment of goodwill |  | 0 | 0 | $ (114,400,000) |  |
Accumulated goodwill impairment |  | 241,000,000.0 | 241,000,000 | 241,000,000 |  |
Addaero Manufacturing [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill |  |  | 6,000,000.0 |  |  |
Payments to Acquire Businesses, Gross | $ 10,000,000.0 |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles |  |  | $ 2,000,000.0 |  |  |
High Performance Materials & Components |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill |  | 525,800,000 |  |  |  |
Impairment of goodwill |  | 0 |  | $ (114,400,000) |  |
Goodwill, Foreign Currency Translation Gain (Loss) |  | 1,500,000 |  |  |  |
High Performance Materials & Components | First Reporting Unit [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Percentage of fair value in excess of carrying value |  |  |  |  |  | 12.00%
Forged Products |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Goodwill |  | $ (10,400,000) |  |  | $ 10,400,000 |

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