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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