Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 1	$ 1	$ 2	$ 2
Operating Expenses - Other taxes from affiliate		2	2	5	4
D E S And D E S S
Related Party Transaction [Line Items]
Purchases from affiliate	[1]	51	57	106	115
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		$ 5	$ 5	$ 7	$ 7

[1] Includes capitalized expenditures of $12 million and $10 million for the three months ended June 30, 2022 and 2021, respectively, and $24 million and $15 million for the six months ended June 30, 2022 and 2021, respectively.