v3.19.1
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Fair Value Measurement [Domain]      
Fair Value Disclosures [Abstract]      
Cash and Cash Equivalents, at Carrying Value $ 19   $ 23
Restricted Cash and Cash Equivalents 156   145
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs (8) $ 197  
Included in operating revenues [1] 50 (57)  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Gain (Loss) Included In Fuel And Purchased Energy Expense [2] 2 (2)  
Amount of Change in Collateral of Financial Instruments Classified as Derivative Asset (Liability) 2 (2)  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases 2 4  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 58 (14)  
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount 0 0  
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount 0 0  
Transfers into level 3 [3],[4] (1) 6  
Transfers out of Level 3 [4],[5] 0 (3)  
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs 105 129  
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) 52 $ (59)  
Cash and Cash Equivalents, at Carrying Value 184   205
Restricted Cash and Cash Equivalents 334   201
Fair Value, Inputs, Level 1 [Member]      
Fair Value Disclosures [Abstract]      
Derivative, Collateral, Right to Reclaim Cash, Net 76   (1)
Fair Value, Inputs, Level 2 [Member]      
Fair Value Disclosures [Abstract]      
Derivative, Collateral, Right to Reclaim Cash, Net 47   48
Fair Value, Inputs, Level 3 [Member]      
Fair Value Disclosures [Abstract]      
Derivative, Collateral, Right to Reclaim Cash, Net $ 2   $ 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 $(1) million in losses and $6 million in gains transferred out of level 2 into level 3 for the three months ended March 31, 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 months ended March 31, 2019 and 2018.
[5] We had nil and $3 million in gains transferred out of level 3 into level 2 for the three months ended March 31, 2019 and 2018, respectively, due to changes in market liquidity in various power markets.