Derivative Financial Instruments (Derivatives Not Designated as Hedging Instruments) (Detail) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (2)	$ 15	$ (1)	$ 17
Commodity Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (1)	$ 15	$ 0	$ 18
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	Utilities Operating Expense Purchased Power
Interest Rate Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (1)	$ 0	$ (1)	$ (1)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Interest Expense	Interest Expense	Interest Expense	Interest Expense

[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.