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Investment in Knife River (Details 3) - USD ($) $ in Thousands, shares in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2023 | Sep. 30, 2022 | May 31, 2023
Fair value, balance sheet grouping [Line Items] |  |  |  |
Retained Shares Ownership Percentage |  |  |  | 10.00%
Retained Shares |  |  |  | 5.7
Unrealized Gain (Loss) on Investments |  | $ 3,501 | $ (12,357) |
Investment in Knife River |  |  |  |
Fair value, balance sheet grouping [Line Items] |  |  |  |
Investments, Fair Value Disclosure | $ 276,200 | 276,200 |  |
Unrealized Gain (Loss) on Investments | $ 30,200 | $ 170,200 |  |

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- Definition Percentage of shares retained in Knife River + References No definition available. + Details
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