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Restructuring Costs (Details) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2016 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) employee
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  | $ 0.0 | $ 0.0 | $ 523.8
Revision of estimates |  | 0.0 | 0.1 |
Restructuring and other charges |  | $ 0.0 | $ 0.0 | 538.5
SEC Schedule, 12-09, Reserve, Inventory | Industrial titanium products |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Inventory valuation charges |  |  |  | 17.7
Long-lived asset impairment [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | 471.3
Facility Closing [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | 31.7
Employee benefit costs [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | $ 20.8
Flat Rolled Products |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and Related Cost, Expected Number of Positions Eliminated | employee |  |  |  | 250
Flat Rolled Products | Facility Closing [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | $ 8.4
Flat Rolled Products | Employee benefit costs [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | 4.9
Flat Rolled Products | Special Termination Benefits [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | 3.4
Flat Rolled Products | Employee Severance [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | $ 11.8
High Performance Materials & Components |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and Related Cost, Expected Number of Positions Eliminated | employee |  |  |  | 180
High Performance Materials & Components | Facility Closing [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | $ 23.8
High Performance Materials & Components | Employee benefit costs [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring charges |  |  |  | 7.5
Rowley, UT facility [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Asset Impairment Charges | $ 470.8 |  |  |
Estimated fair value after impairment |  |  |  | $ 15.0

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