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Borrowings and Other Financing Instruments Borrowings and Other Financing Instruments, Letters of Credit (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Line of Credit Facility [Line Items]    
Amount outstanding at period end $ 83 $ 19
Long-term Debt    
Line of Credit Facility [Line Items]    
Debt Instrument, Face Amount 1 0
Letter of Credit    
Line of Credit Facility [Line Items]    
Amount outstanding at period end $ 0 0
Letter of Credit    
Line of Credit Facility [Line Items]    
Line of Credit Facility, Expiration Period 1 year  
Credit Facilities    
Line of Credit Facility [Line Items]    
Long-term Line of Credit $ 0 $ 0