Derivatives and Other Financial Instruments - Schedule of Net Fair Values of Level 3 Derivative Instruments and Effect of Hypothetical Change (Increase or Decrease of 10%) in Market Prices or Rates (Detail) $ in Millions	Dec. 31, 2021 USD ($)
Power Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value asset (liability)	$ (1,290)
Index change of + / -10%	357
Embedded Credit Derivative [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value asset (liability)	(3)
Index change of + / -10%	1
Financial Contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value asset (liability)	2
Index change of + / -10%	$ 7