Derivatives and Other Financial Instruments - Schedule of Fair Values of Level 3 Derivative Instruments Recorded as Assets and Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Derivative Instruments Gain Loss [Line Items]
Total Asset Derivatives	$ 14	$ 2
Fair value liability derivatives	2,024	1,293
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Total Asset Derivatives	14	2
Fair value liability derivatives	1	3
Derivatives Not Designated as Hedging Instruments [Member] | Fair Value of Derivative Contracts - Current [Member] | Financial Contracts [Member]
Derivative Instruments Gain Loss [Line Items]
Total Asset Derivatives	14	2
Derivatives Not Designated as Hedging Instruments [Member] | Fair Value of Derivative Contracts - Current [Member] | Embedded Credit Derivative [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value liability derivatives		1
Derivatives Not Designated as Hedging Instruments [Member] | Fair Value of Derivative Contracts - Noncurrent [Member] | Embedded Credit Derivative [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value liability derivatives	1	2
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value liability derivatives	2,023	1,290
Derivatives Designated as Hedging Instruments [Member] | Fair Value of Derivative Contracts - Current [Member] | Power Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value liability derivatives	386	262
Derivatives Designated as Hedging Instruments [Member] | Fair Value of Derivative Contracts - Noncurrent [Member] | Power Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Fair value liability derivatives	$ 1,637	$ 1,028