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Nature of Operations And Summary of Significant Accounting Policies (Narrative) (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Basis Of Accounting Presentation [Line Items]      
Number of customers 3,800,000    
Other than Temporary Impairment Losses, Investments $ 0.0 $ 0.0 $ 0.0
Pre-tax rate for allowance for funds used during construction 3.90% 3.40% 3.30%
Inventory valued using LIFO $ 43.9 $ 43.0  
Excess of replacement over LIFO value (22.5) (7.7)  
Inventory valued using the weighted average cost methodology $ 222.0 $ 488.7