Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 2	$ 2	$ 3	$ 3
Operating Revenues - Gas from sales to affiliate		1	1	1	1
Operating Expenses - Other taxes from affiliate		2	2	5	5
Related Party | DES
Related Party Transaction [Line Items]
Direct and allocated costs	[1]	58	57	120	110
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		$ 4	$ 3	$ 7	$ 4

[1] Includes capitalized expenditures of $19 million and $15 million for the three months ended June 30, 2025 and 2024, respectively, and $38 million and $27 million for the six months ended June 30, 2025 and 2024, respectively.