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Other - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Public Utilities General Disclosures [Line Items]      
Sales to TEC $ 0 $ 0  
Sales to Non member 0 $ 0  
Revolving Credit Facility      
Public Utilities General Disclosures [Line Items]      
Line of credit outstanding 0   $ 0
Revolving Credit Facility | Through March 3, 2022 [Member]      
Public Utilities General Disclosures [Line Items]      
Credit facility, maximum borrowing capacity 500,000,000    
Revolving Credit Facility | March 4, 2022 through February 28, 2025 [Member]      
Public Utilities General Disclosures [Line Items]      
Credit facility, maximum borrowing capacity 400,000,000    
Letter of Credit [Member]      
Public Utilities General Disclosures [Line Items]      
Line of credit outstanding $ 500,000   $ 500,000