Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
Financial Contracts [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets, Beginning balance	$ 34	$ 16
Fair value measurement, Assets	(8)
Other expenses, net (unrealized/realized)	(8)
Settlements and other	(25)	(57)
Fair value measurement, Assets, Ending balance	$ 1	1
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Costs And Operating Expenses And Nonoperating Income Expenses
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Costs And Operating Expenses And Nonoperating Income Expenses
Financial Contracts [Member] | Other Expenses, Net [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets		42
Financial Contracts [Member] | Other Expenses, Net [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets		42
Power Contract [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Settlements and other	$ 0	0
Fair value measurement, Liabilities, Beginning balance	1,190	1,297
Fair value measurement, Liabilities	$ 0	$ 0
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Other comprehensive income (unrealized)	$ 149	$ 174
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax
Fair value measurement, Liabilities, Ending balance	$ 1,266	$ 1,266
Power Contract [Member] | Sales [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Liabilities	(73)	(205)
Power Contract [Member] | Other Expenses, Net [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Liabilities	0	0
Embedded Credit Derivative [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Settlements and other	(1)	(1)
Fair value measurement, Liabilities, Beginning balance	1	0
Fair value measurement, Liabilities	$ 2	$ 3
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Other comprehensive income (unrealized)	$ 0	$ 0
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax
Fair value measurement, Liabilities, Ending balance	$ 2	$ 2
Embedded Credit Derivative [Member] | Sales [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Liabilities	0	0
Embedded Credit Derivative [Member] | Other Expenses, Net [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement, Liabilities	$ 2	$ 3