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Fair Value of Financial Assets and Liabilities - Impact of Derivative Activities on Income (Details)
MMBTU in Millions, $ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2022
USD ($)
MMBTU
Jun. 30, 2021
USD ($)
Jun. 30, 2022
USD ($)
MMBTU
Jun. 30, 2021
USD ($)
Dec. 31, 2021
MMBTU
Derivative Instruments, Gain (Loss) [Line Items]          
Derivative instruments designated as fair value hedges $ 0 $ 0 $ 0 $ 0  
Financial Impact of Qualifying Fair Value Hedges on Earnings [Abstract]          
Derivative instruments designated as fair value hedges $ 0 0 $ 0 0  
Natural Gas Commodity [Member]          
Derivative Instruments, Gain (Loss) [Line Items]          
Derivative, Nonmonetary Notional Amount | MMBTU 0   0   0
Other Derivative Instruments | Natural Gas Commodity          
Derivative Instruments, Gain (Loss) [Line Items]          
Pre-tax (gains) losses reclassified into income during the period from regulatory assets and (liabilities) $ 0 0 $ (1) (1)  
Other Derivative Instruments | Electric Commodity Contract          
Derivative Instruments, Gain (Loss) [Line Items]          
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities   $ 0   $ 1