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Risk Management and Derivatives: Derivatives by Balance Sheet Classification (Details) - USD ($) $ in Millions | Sep. 30, 2024 | Dec. 31, 2023
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Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | $ (0.6) | $ (2.9)
Commodity Contract | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | (4.0) | (3.9)
Other assets, non-current | Commodity Contract | Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Liability, Fair Value, Gross Liability | 0.0 | (0.2)
Derivative liabilities, current | Commodity Contract | Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Liability, Fair Value, Gross Liability | (0.6) | (2.7)
Derivative liabilities, current | Commodity Contract | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Liability, Fair Value, Gross Liability | (3.9) | (3.8)
Other deferred credits and other liabilities | Commodity Contract | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Derivative Liability, Fair Value, Gross Liability | $ (0.1) | $ (0.1)

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- Definition Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 9 -SubTopic 20 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-9 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -SubTopic 20 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483466/210-20-50-3 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 10 -SubTopic 20 -Topic 210 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-10 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-8 + Details
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