Derivative Financial Instruments (Derivatives Not Designated as Hedging Instruments) (Detail) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ 1	$ 2
Commodity Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ 1	$ 3
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		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]	$ 0	$ (1)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		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.