v3.26.1
Derivatives and Other Financial Instruments - Schedule of Fair Values of Level 3 Derivative Instruments Recorded as Assets and Liabilities (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Derivative Instruments Gain Loss [Line Items]    
Total asset derivatives $ 83 $ 49
Total asset derivatives 25 34
Total liability derivatives 494 467
Total liability derivatives 880 1,134
Level 3 [Member] | Energy Contracts [Member]    
Derivative Instruments Gain Loss [Line Items]    
Total asset derivatives 16 20
Total liability derivatives 1,222 1,354
Level 3 [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Energy Contracts [Member]    
Derivative Instruments Gain Loss [Line Items]    
Total asset derivatives 16 20
Total liability derivatives 22 0
Level 3 [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Financial Contracts [Member] | Energy Contracts [Member]    
Derivative Instruments Gain Loss [Line Items]    
Total asset derivatives 11 15
Total asset derivatives 5 5
Total liability derivatives 22 0
Level 3 [Member] | Derivatives Designated as Hedging Instruments [Member] | Energy Contracts [Member]    
Derivative Instruments Gain Loss [Line Items]    
Total liability derivatives 1,200 1,354
Level 3 [Member] | Derivatives Designated as Hedging Instruments [Member] | Power Contract [Member] | Energy Contracts [Member]    
Derivative Instruments Gain Loss [Line Items]    
Total liability derivatives 376 353
Total liability derivatives $ 824 $ 1,001