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Supplemental Financial Statement Information - Schedule of Other Income, Net (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Other Income and Expenses [Abstract] |  |  |  |
Rent and royalty income | $ 0.2 | $ 0.7 | $ 0.5 | $ 1.4
Gains from disposal of property, plant and equipment, net | 0.0 | 29.1 | 2.5 | 28.3
Net equity (loss) gain on joint ventures | (1.9) | (3.5) | (5.6) | (6.3)
Loss from sale of businesses | 0.0 | (7.7) | 0.0 | (7.7)
Adjustment to indemnification for conditional ARO costs | 4.3 | 0.0 | 4.3 | 0.0
Other | 0.3 | 0.0 | 0.3 | 0.0
Other income (expense), net | 0.5 | 18.6 | (0.4) | 15.7
Allegheny & Tsingshan Stainless | Employee Severance [Member] |  |  |  |
Other Income and Expenses [Abstract] |  |  |  |
Net equity (loss) gain on joint ventures | $ (2.4) | $ 0.0 | $ (2.4) | $ 0.0

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