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Risk Management and Derivatives: Derivatives Not Designated as Hedge Instruments (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Derivative [Line Items] |  |  |  |  |
Regulatory assets | $ 271,236 |  | $ 271,236 |  | $ 271,344
Gas price derivatives |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Regulatory assets | 499 |  | 499 |  | $ 3,328
Not Designated as Hedging Instrument |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | 391 | $ 122 | 2,764 | $ (1,038) |
Not Designated as Hedging Instrument | Fuel, purchased power and cost of natural gas sold | Electricity |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | (1,386) | 142 | (228) | 142 |
Not Designated as Hedging Instrument | Fuel, purchased power and cost of natural gas sold | Natural Gas, Distribution |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | $ 1,777 | $ (20) | $ 2,992 | $ (1,180) |

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
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