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WUTC (Details 4) - Cascade Natural Gas [Member] - WUTC [Member] - USD ($) | Mar. 01, 2020 | Nov. 01, 2019 | May 31, 2019 | Mar. 29, 2019
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Distribution |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ 12,700,000
Public Utilities, Requested Rate Increase (Decrease), Percentage |  |  |  | 5.50%
Pipeline Cost Recovery Mechanism [Member] |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  | $ 1,600,000 |
Public Utilities, Requested Rate Increase (Decrease), Percentage |  |  | 0.70% |
Public Utilities, Approved Rate Increase (Decrease), Amount |  | $ 440,000 |  |
Public utilities, approved rate increase (decrease), percentage |  | 0.20% |  |
Purchased Gas Adjustment [Member] |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  | $ 12,800,000 |  |
Public utilities, approved rate increase (decrease), percentage |  | 5.70% |  |
Regulatory Asset, Amortization Period |  | 3 years |  |
Subsequent Event [Member] | Distribution |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount | $ 6,500,000 |  |  |
Public utilities, approved rate increase (decrease), percentage | 2.80% |  |  |

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