XML 23 R60.htm IDEA: XBRL DOCUMENT v3.19.3
Fair Value (Unobservable Inputs related to Level 3 Assets and Liabilities) (Details)
$ in Millions
Sep. 30, 2019
USD ($)
$ / MWh
$ / MMBTU
Dec. 31, 2018
USD ($)
$ / MWh
$ / MMBTU
Unobservable Inputs Valuation Techniques [Line Items]    
Derivative Assets $ 429 $ 663
Derivative Liabilities (460) (669)
Recurring | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Derivative Assets 95 126
Derivative Liabilities (123) (170)
Natural gas    
Unobservable Inputs Valuation Techniques [Line Items]    
Derivative Assets 253 349
Derivative Liabilities (297) (380)
Natural gas | Recurring | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Derivative Assets 54 63
Derivative Liabilities (95) (112)
Electricity    
Unobservable Inputs Valuation Techniques [Line Items]    
Derivative Assets 164 303
Derivative Liabilities (155) (285)
Electricity | Recurring | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Derivative Assets 36 56
Derivative Liabilities $ (28) $ (58)
Forward basis price | Natural gas | Minimum | Discounted Cash Flow | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Forward basis price | $ / MMBTU (1.55) (2.15)
Forward basis price | Natural gas | Maximum | Discounted Cash Flow | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Forward basis price | $ / MMBTU 6.17 5.59
Forward basis price | Natural gas | Weighted Average | Discounted Cash Flow | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Forward basis price | $ / MMBTU (0.09) (0.10)
Forward basis price | Electricity | Minimum | Discounted Cash Flow | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Forward basis price | $ / MWh (13) (7)
Forward basis price | Electricity | Maximum | Discounted Cash Flow | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Forward basis price | $ / MWh 7 9
Forward basis price | Electricity | Weighted Average | Discounted Cash Flow | Level 3    
Unobservable Inputs Valuation Techniques [Line Items]    
Forward basis price | $ / MWh 0 1