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Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($) $ in Millions | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | $ 5.0 | $ 18.8
Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 46.5 | 66.0
Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 5.4 | 1.1
Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 1.1 | 1.9
Interest Rate Risk | Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 0.0 | 0.0
Interest Rate Risk | Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 0.0 | 0.0
Interest Rate Risk | Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 0.0 | 0.0
Interest Rate Risk | Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 0.0 | 0.0
Commodity Price Risk Programs | Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 5.0 | 18.8
Commodity Price Risk Programs | Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 46.5 | 66.0
Commodity Price Risk Programs | Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 5.4 | 1.1
Commodity Price Risk Programs | Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | $ 1.1 | $ 1.9

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