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Borrowings and Other Financing Instruments, Letters of Credit (Details) - USD ($)
3 Months Ended
Mar. 31, 2023
Dec. 31, 2022
Line of Credit Facility [Line Items]    
Line of Credit Facility, Expiration Period 1 year  
Amount outstanding at period end $ 12,000,000 $ 47,000,000
Credit Facility    
Line of Credit Facility [Line Items]    
Long-term Line of Credit $ 0 $ 0