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Risk Management and Derivatives: Derivatives by Balance Sheet Classification (Details) - Commodity Contracts - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
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Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedges, Net | $ 520 | $ (515)
Designated as Hedging Instrument | Derivative assets — current |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Assets | 435 | 1
Designated as Hedging Instrument | Other assets, non-current |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Assets | 94 | 3
Designated as Hedging Instrument | Derivative liabilities — current |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Liabilities | (9) | (490)
Designated as Hedging Instrument | Other deferred credits and other liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Liabilities | 0 | (29)
Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedges, Net | 570 | (1,484)
Not Designated as Hedging Instrument | Derivative assets — current |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Assets | 1,566 | 341
Not Designated as Hedging Instrument | Other assets, non-current |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Assets | 434 | 2
Not Designated as Hedging Instrument | Derivative liabilities — current |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Liabilities | (1,430) | (1,764)
Not Designated as Hedging Instrument | Other deferred credits and other liabilities |  |
Derivatives, Fair Value [Line Items] |  |
Fair Value Hedge Liabilities | $ 0 | $ (63)

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