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Property, Plant, Equipment and Mine Development (Tables) | 6 Months Ended
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Jun. 30, 2023
Property, Plant and Equipment [Abstract] |
Schedule of Property, Plant, Equipment and Mine Development | The composition of property, plant, equipment and mine development, net, as of June 30, 2023 and December 31, 2022 is set forth in the table below:
| June 30, 2023 |  | December 31, 2022
| (Dollars in millions)
Land and coal interests | $ | 2,511.9 |  |  | $ | 2,514.7 |
Buildings and improvements | 628.8 |  |  | 594.2 |
Machinery and equipment | 1,612.0 |  |  | 1,543.1 |
Less: Accumulated depreciation, depletion and amortization | (1,933.2) |  |  | (1,787.0) |
Property, plant, equipment and mine development, net | $ | 2,819.5 |  |  | $ | 2,865.0 |

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- Definition Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 10 -Topic 360 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482099/360-10-50-1 + Details
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