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Minnesota Public Utilities Commission (Details 2) - MNPUC [Member] - Natural gas cost tariff [Member] - USD ($) | Oct. 06, 2017 | Dec. 21, 2016
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Public Utilities, General Disclosures [Line Items] |  |
Public utilities, requested rate increase (decrease), amount |  | $ 456,000
Subsequent event [Member] |  |
Public Utilities, General Disclosures [Line Items] |  |
Public utilities, approved rate increase (decrease), amount | $ 456,000 |

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