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Note 1 - Summary of Significant Accounting Policies - Estimated Useful Lives of Various Classes of Assets (Details) | 12 Months Ended
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Mar. 31, 2021
Building [Member] |
Buildings (in years) (Year) | 20 years
Machinery and Equipment [Member] | Minimum [Member] |
Buildings (in years) (Year) | 10 years
Machinery and Equipment [Member] | Maximum [Member] |
Buildings (in years) (Year) | 15 years
Yard Improvements [Member] | Minimum [Member] |
Buildings (in years) (Year) | 5 years
Yard Improvements [Member] | Maximum [Member] |
Buildings (in years) (Year) | 15 years
Loaders and Other Rolling Stock [Member] | Minimum [Member] |
Buildings (in years) (Year) | 5 years
Loaders and Other Rolling Stock [Member] | Maximum [Member] |
Buildings (in years) (Year) | 15 years

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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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Period Type: | duration

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Balance Type: |
Period Type: |

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- Details
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Balance Type: |
Period Type: |

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- Details
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