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Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($) $ in Millions | Sep. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Risk Management Assets Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | $ 41.8 | $ 10.6
Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 94.4 | 13.8
Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 1.9 | 136.8
Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 1.7 | 7.4
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 | 12.1 | 0.0
Interest Rate Risk | Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 0.0 | 136.4
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 | 41.8 | 10.6
Commodity Price Risk Programs | Risk Management Assets Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management assets | 82.3 | 13.8
Commodity Price Risk Programs | Risk Management Liabilities Current |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | 1.9 | 0.4
Commodity Price Risk Programs | Risk Management Liabilities Noncurrent |  |
Derivatives, Fair Value [Line Items] |  |
Risk management liabilities | $ 1.7 | $ 7.4

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