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Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($)
$ in Millions
Mar. 31, 2025
Dec. 31, 2024
Assets:    
Cash equivalents $ 0 $ 12
Debt securities:    
Domestic government 27 16
Corporate credit 9 7
Money market funds measured at NAV (2) 8 7
Non-qualified benefit plan trust: (2)    
Alternative Investment 5 4
Debt securities—domestic government 2 2
Assets from price risk management activities: (1) (3)    
Electricity 25 19
Natural gas 8 15
Total 13 11
Assets, Fair Value Disclosure 84 82
Liabilities from price risk management activities: (1) (3)    
Electricity 58 56
Natural gas 118 163
Total 176 219
Fair Value, Inputs, Level 1 [Member]    
Assets:    
Cash equivalents 0 12
Debt securities:    
Domestic government 15 10
Corporate credit 0 0
Non-qualified benefit plan trust: (2)    
Debt securities—domestic government 2 2
Assets from price risk management activities: (1) (3)    
Electricity 0 0
Natural gas 0 0
Total 17 24
Liabilities from price risk management activities: (1) (3)    
Electricity 0 0
Natural gas 0 0
Total 0 0
Fair Value, Inputs, Level 2 [Member]    
Assets:    
Cash equivalents 0 0
Debt securities:    
Domestic government 12 6
Corporate credit 9 7
Non-qualified benefit plan trust: (2)    
Debt securities—domestic government 0 0
Assets from price risk management activities: (1) (3)    
Electricity 21 18
Natural gas 8 15
Total 50 46
Liabilities from price risk management activities: (1) (3)    
Electricity 19 25
Natural gas 114 159
Total 133 184
Fair Value, Inputs, Level 3 [Member]    
Assets:    
Cash equivalents 0 0
Debt securities:    
Domestic government 0 0
Corporate credit 0 0
Non-qualified benefit plan trust: (2)    
Debt securities—domestic government 0 0
Assets from price risk management activities: (1) (3)    
Electricity 4 1
Natural gas 0 0
Total 4 1
Liabilities from price risk management activities: (1) (3)    
Electricity 39 31
Natural gas 4 4
Total $ 43 $ 35