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Note 11 - Properties (Details Textual) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Number of Depreciable Asset Classes |  | 60 |  |
Cost of Property Repairs and Maintenance |  | $ 2,100 | $ 2,000 | $ 2,300
Brazos Yard [Member] | Other Expense [Member] |  |  |  |
Asset Impairment Charges, Total | $ 278 |  |  |
Railroad Transportation Equipment [Member] |  |  |  |
Term of Depreciation Studies (Year) |  | 3 years |  |
Railroad Transportation Track Assets [Member] |  |  |  |
Term of Depreciation Studies (Year) |  | 6 years |  |

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