Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 1	$ 0	$ 3	$ 2
Operating Revenues - Gas from sales to affiliate		1	0	1	0
Operating Expenses - Other taxes from affiliate		1	2	6	6
D E S And D E S S
Related Party Transaction [Line Items]
Purchases from affiliate	[1]	52	53	158	168
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		$ 5	$ 5	$ 12	$ 12

[1] Includes capitalized expenditures of $12 million and $8 million for the three months ended September 30, 2022 and 2021, respectively, and $36 million and $23 million for the nine months ended September 30, 2022 and 2021, respectively.