Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Derivative assets with affiliates	$ 56	$ 28
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Payable to affiliates	1	1
Nuclear Affiliates [Member]
Related Party Transaction [Line Items]
Receivable from affiliates		1
D E S And D E S S
Related Party Transaction [Line Items]
Payable to affiliates	23	30
Dominion Energy
Related Party Transaction [Line Items]
Payable to affiliates	48	1
Receivable from affiliates	2
Public Service Company Of North Carolina Incorporated
Related Party Transaction [Line Items]
Payable to affiliates	9
Receivable from affiliates		$ 60
SCANA Corporation
Related Party Transaction [Line Items]
Payable to affiliates	$ 7