Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions		Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 135		$ 115
Derivative assets with affiliates	[1]		$ 33	51
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Affiliated and related party payables and other			1	0
Dominion Energy | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other			2	1
DES | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other			18	22
SCANA Corporation | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other			7	7
Public Service Company Of North Carolina Incorporated | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other			$ 9	$ 12

[1] Includes amounts recorded in other current assets of $4 million and $8 million as of September 30, 2023 and December 31, 2022, respectively, and amounts recorded in other deferred debits and other assets of $29 million and $43 million as of September 30, 2023 and December 31, 2022, respectively.