Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 1	$ 1	$ 3	$ 3
Operating Revenues – Gas from sales to affiliate		1	1	1	1
Operating Expenses - Other taxes from affiliate		2	1	7	6
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		5	5	11	12
Related Party | DES
Related Party Transaction [Line Items]
Direct and allocated costs	[1]	$ 53	$ 52	$ 165	$ 158

[1] Includes capitalized expenditures of $15 million and $12 million for the three months ended September 30, 2023 and 2022, respectively and $44 million and $36 million for the nine months ended September 30, 2023 and 2022.