v3.20.1
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Fair Value Measurement [Domain]      
Fair Value Disclosures [Abstract]      
Cash and Cash Equivalents, at Carrying Value $ 222   $ 573
Restricted Cash and Cash Equivalents 222   211
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 171 $ (8)  
Included in operating revenues [1] 81 50  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Gain (Loss) Included In Fuel And Purchased Energy Expense [2] (4) 2  
Amount of Change in Collateral of Financial Instruments Classified as Derivative Asset (Liability) 0 2  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases 0 2  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 0 58  
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount   0  
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount 0 0  
Transfers into level 3 [3],[4] 3 (1)  
Transfers out of Level 3 [3],[5] (2) 0  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 249 105  
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) 77 $ 52  
Cash and Cash Equivalents, at Carrying Value 531   1,131
Restricted Cash and Cash Equivalents 306   345
Level 1      
Fair Value Disclosures [Abstract]      
Derivative, Collateral, Right to Reclaim Cash, Net 35   112
Level 2      
Fair Value Disclosures [Abstract]      
Derivative, Collateral, Right to Reclaim Cash, Net 8   2
Level 3      
Fair Value Disclosures [Abstract]      
Derivative, Collateral, Right to Reclaim Cash, Net $ 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 $3 million in gains and $(1) million in losses transferred out of level 2 into level 3 for the three months ended March 31, 2020 and 2019, respectively, due to changes in market liquidity in various power markets.
[5] We had $2 million in gains and nil transferred out of level 3 into level 2 for the three months ended March 31, 2020 and 2019, respectively, due to changes in market liquidity in various power markets.