Derivative Financial Instruments (Derivatives Not Designated as Hedging Instruments) (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ 4	$ 75	$ 6
Commodity Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ 6	$ 77	$ 8
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Utilities Operating Expense, Purchased Power	Utilities Operating Expense, Purchased Power	Utilities Operating Expense, Purchased Power
Interest Rate Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (2)	$ (2)	$ (2)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Interest expense from money pool transactions	Interest expense from money pool transactions	Interest expense from money pool transactions

[1] Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.