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Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Risk Management Assets Current    
Derivatives, Fair Value [Line Items]    
Risk management assets $ 3.0 $ 1.1
Risk Management Assets Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 20.2 22.2
Risk Management Liabilities Current    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 11.6 7.5
Risk Management Liabilities Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 1.9 1.9
Commodity Price Risk Programs | Risk Management Assets Current    
Derivatives, Fair Value [Line Items]    
Risk management assets 3.0 1.1
Commodity Price Risk Programs | Risk Management Assets Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 20.2 22.2
Commodity Price Risk Programs | Risk Management Liabilities Current    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 11.6 7.5
Commodity Price Risk Programs | Risk Management Liabilities Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities $ 1.9 $ 1.9