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WUTC (Details 5) - Pending Rate Case [Member] - Gas Distribution [Member] - WUTC [Member] - Cascade Natural Gas [Member] - USD ($) $ in Millions | Jan. 08, 2021 | Jul. 24, 2020 | Jun. 19, 2020
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Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  | $ 13.8
Public Utilities, Requested Rate Increase (Decrease), Percentage |  |  | 5.30%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount |  | $ 14.3 |
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage |  | 5.50% |
Subsequent Event [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount | $ 7.4 |  |
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage | 2.80% |  |

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