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Derivatives, Hedging Programs and Other Financial Instruments, Narrative (Details) - USD ($)
9 Months Ended
Sep. 30, 2019
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Derivative [Line Items]                
Collateral posted for net derivatives $ 0             $ 0
Document Period End Date Sep. 30, 2019              
Maturity period of short-term investments 12 months              
Customer Deposits, Current $ 200,000             200,000
Designated as Hedging Instrument | Purchase                
Derivative [Line Items]                
Derivative net liability $ 13,700,000             $ 12,600,000
Scenario, Forecast | Natural Gas                
Derivative [Line Items]                
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage   77.00% 83.00% 83.00% 68.00% 68.00% 72.00%  
Scenario, Forecast | Electricity                
Derivative [Line Items]                
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage         46.00% 55.00% 54.00%