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Business Segments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Segment Reporting Information [Line Items] |  |  |  |
Sales | $ 725.7 | $ 598.0 | $ 2,034.4 | $ 2,323.8
Segment EBITDA | 94.2 | 27.8 | 241.7 | 207.6
LIFO and net realizable value reserves | 0.0 | 0.0 | 0.0 | 0.0
Corporate expenses | (12.9) | (10.2) | (41.0) | (29.7)
Closed operations and other expense | (1.4) | (1.0) | (4.5) | (4.6)
Total ATI Adjusted EBITDA | 79.9 | 16.6 | 196.2 | 173.3
Depreciation & amortization | (35.6) | (35.4) | (108.0) | (108.3)
Interest expense, net | (25.1) | (25.1) | (72.2) | (68.7)
Restructuring charges (credits) | (2.3) | 2.3 | (8.5) | 27.0
Strike related costs | (22.9) | 0.0 | (63.2) | 0.0
Retirement benefit settlement gain | 64.9 | 0.0 | 64.9 | 0.0
Impairment of goodwill | 0.0 | 0.0 | 0.0 | (287.0)
Income (loss) from equity investments | 0.4 | (1.0) | 0.4 | (6.6)
Debt extinguishment charge | 0.0 | 0.0 | 0.0 | (21.5)
Gain on asset sales and sale of business | 13.7 | 0.0 | 13.7 | 2.5
Income (loss) before income taxes | 77.2 | (46.2) | 39.9 | (339.1)
Employee Severance [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Restructuring charges (credits) |  |  | (9.2) |
Allegheny & Tsingshan Stainless | Employee Severance [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Income (loss) from equity investments | 0.0 | 0.0 | 0.0 | (2.4)
Advanced Alloys & Solutions [Member] | Allegheny & Tsingshan Stainless |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Income (loss) from equity investments | 0.3 | (1.6) | (0.6) | (10.1)
Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 789.7 | 623.4 | 2,189.0 | 2,482.4
Depreciation & amortization | (35.6) | (35.4) | (108.0) | (108.3)
Operating Segments | High Performance Materials & Components |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 325.0 | 230.1 | 908.9 | 995.3
Segment EBITDA | 37.4 | 16.8 | 99.2 | 122.1
Depreciation & amortization | (18.2) | (19.5) | (57.0) | (58.5)
Strike related costs | (1.4) |  | (3.5) |
Operating Segments | Advanced Alloys & Solutions [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 464.7 | 393.3 | 1,280.1 | 1,487.1
Segment EBITDA | 56.8 | 11.0 | 142.5 | 85.5
Depreciation & amortization | (16.3) | (15.1) | (47.9) | (47.4)
Strike related costs | (21.5) |  | (59.7) |
Operating Segments | Corporate Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Depreciation & amortization | (1.1) | (0.8) | (3.1) | (2.4)
Internal Customers | Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 64.0 | 25.4 | 154.6 | 158.6
Internal Customers | Operating Segments | High Performance Materials & Components |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 25.0 | 8.8 | 67.4 | 53.0
Internal Customers | Operating Segments | Advanced Alloys & Solutions [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 39.0 | 16.6 | 87.2 | 105.6
External Customers | Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 725.7 | 598.0 | 2,034.4 | 2,323.8
External Customers | Operating Segments | High Performance Materials & Components |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | 300.0 | 221.3 | 841.5 | 942.3
External Customers | Operating Segments | Advanced Alloys & Solutions [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Sales | $ 425.7 | $ 376.7 | $ 1,192.9 | $ 1,381.5

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