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Revenues - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Disaggregation of Revenue [Line Items]        
Typical length of contract     Electricity and natural gas products may be sold as fixed-price or variable-price products. The typical length of a contract to provide electricity and/or natural gas is twelve months.  
Electric and Gas Revenue        
Disaggregation of Revenue [Line Items]        
Excise and Sales Taxes $ 0.2 $ 0.4 $ 0.5 $ 0.7
Cost of Services Energy Services        
Disaggregation of Revenue [Line Items]        
Excise and Sales Taxes $ 1.0 $ 1.4 $ 2.2 $ 3.1