Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 1	$ 1
Operating Expenses - Other taxes from affiliate		3	3
DES
Related Party Transaction [Line Items]
Direct and allocated costs	[1]	57	55
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		$ 2	$ 2

[1] Includes capitalized expenditures of $16 million and $12 million for the three months ended March 31, 2023 and 2022, respectively.