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Accounting Policies - Accrued Unbilled Revenue (Details 3) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Accounting Policies [Abstract] |  |
Accrued unbilled revenue at MDU Energy Capital | $ 94.0 | $ 100.8

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- Definition Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer. + References No definition available. + Details
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