v3.20.2
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Mar. 31, 2019
Fair Value Measurement [Domain]            
Fair Value Disclosures [Abstract]            
Cash and Cash Equivalents, at Carrying Value $ 190   $ 190   $ 573  
Restricted Cash and Cash Equivalents 227   227   211  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 249 $ 105 171 $ (8)    
Included in operating revenues [1] 37 152 106 197    
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Gain (Loss) Included In Fuel And Purchased Energy Expense [2] 3 1 (1) 2    
Amount of Change in Collateral of Financial Instruments Classified as Derivative Asset (Liability) 0 (1) 0 1    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases 1 1 1 3    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Issues 0 (1) 0 (1)    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (49) (35) (36) 28    
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount           $ 0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount 0   0     $ 0
Transfers into level 3 [3],[4] 10 6 11 7    
Transfers out of Level 3 [3],[5] (5) (1) (6) (2)    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 246 227 246 227    
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) 40 $ 153 105 $ 199    
Cash and Cash Equivalents, at Carrying Value 677   677   1,131  
Restricted Cash and Cash Equivalents 241   241   345  
Level 1            
Fair Value Disclosures [Abstract]            
Derivative, Collateral, Right to Reclaim Cash, Net 10   10   112  
Level 2            
Fair Value Disclosures [Abstract]            
Derivative, Collateral, Right to Reclaim Cash, Net (3)   (3)   2  
Level 3            
Fair Value Disclosures [Abstract]            
Derivative, Collateral, Right to Reclaim Cash, Net $ 0   $ 0   $ 0  
[1] For power contracts and other power-related products, included on our Consolidated Condensed Statements of Operations.
[2] For natural gas and power contracts, swaps and options, included on our Consolidated Condensed Statements of Operations.
[3] (2)Amount represents the arithmetic average of the significant unobservable input based on the range disclosed.
[4] We had $10 million and $6 million in gains transferred out of level 2 into level 3 for the three months ended June 30, 2020 and 2019, respectively, and $11 million and $7 million in gains transferred out of level 2 into level 3 for the six months ended June 30, 2020 and 2019, respectively, due to changes in market liquidity in various power markets.
[5] We had $5 million and $1 million in gains transferred out of level 3 into level 2 for the three months ended June 30, 2020 and 2019, respectively, and $6 million and $2 million in gains transferred out of level 3 into level 2 for the six months ended June 30, 2020 and 2019, respectively, due to changes in market liquidity in various power markets.