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Summary of Significant Accounting Policies - Estimated Useful Life of Property, Plant and Equipment (Detail) | 6 Months Ended
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Jun. 30, 2018
Land improvements |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 10 years
Plant and buildings | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 5 years
Plant and buildings | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 15 years
Real estate properties | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 10 years
Real estate properties | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 40 years
Railroad and sidings |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 30 years
Vehicles | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 3 years
Vehicles | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 5 years
Machinery, equipment and tooling | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 3 years
Machinery, equipment and tooling | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 15 years
Furniture and fixtures | Minimum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 3 years
Furniture and fixtures | Maximum |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 10 years
Deferred stripping costs |
Property, Plant and Equipment [Line Items] |
Property, plant and equipment, useful life | 3 years

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
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- Details
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Balance Type: |
Period Type: |

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- Details
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- Details
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- Details
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Data Type: | na
Balance Type: |
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- Details
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- Details
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- Details
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- Details
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- Details
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