v3.19.2
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Fair Value Measurement [Domain]          
Fair Value Disclosures [Abstract]          
Cash and Cash Equivalents, at Carrying Value $ 16   $ 16   $ 23
Restricted Cash and Cash Equivalents 149   149   145
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 105 $ 129 (8) $ 197  
Included in operating revenues [1] 152 31 197 (28)  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Gain (Loss) Included In Fuel And Purchased Energy Expense [2] 1 18 2 15  
Amount of Change in Collateral of Financial Instruments Classified as Derivative Asset (Liability) (1) 1 1 (1)  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases 1 5 3 9  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Issues (1) 0 (1) 0  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (35) (42) 28 (53)  
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount 0 0 0 0  
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount 0 0 0 0  
Transfers into level 3 [3],[4] 6 (1) 7 (1)  
Transfers out of Level 3 [4],[5] (1) (10) (2) (7)  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 227 131 227 131  
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) 153 $ 49 199 $ (13)  
Cash and Cash Equivalents, at Carrying Value 297   297   205
Restricted Cash and Cash Equivalents 262   262   201
Fair Value, Inputs, Level 1 [Member]          
Fair Value Disclosures [Abstract]          
Derivative, Collateral, Right to Reclaim Cash, Net 90   90   (1)
Fair Value, Inputs, Level 2 [Member]          
Fair Value Disclosures [Abstract]          
Derivative, Collateral, Right to Reclaim Cash, Net 55   55   48
Fair Value, Inputs, Level 3 [Member]          
Fair Value Disclosures [Abstract]          
Derivative, Collateral, Right to Reclaim Cash, Net $ 1   $ 1   $ 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] We had $6 million in gains and $(1) million in losses transferred out of level 2 into level 3 for the three months ended June 30, 2019 and 2018, respectively, and $7 million in gains and $(1) million in losses transferred out of level 2 into level 3 for the six months ended June 30, 2019 and 2018, respectively, due to changes in market liquidity in various power markets.
[4] We transfer amounts among levels of the fair value hierarchy as of the end of each period. There were no transfers into or out of level 1 for each of the three and six months ended June 30, 2019 and 2018.
[5] We had $1 million and $10 million in gains transferred out of level 3 into level 2 for the three months ended June 30, 2019 and 2018, respectively, and $2 million and $7 million in gains transferred out of level 3 into level 2 for the six months ended June 30, 2019 and 2018, respectively, due to changes in market liquidity in various power markets.