Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions		Jun. 30, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 132	$ 201
Derivative assets with affiliates	[1]	33	48
DES | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		16	19
SCANA Corporation | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 7	$ 7

[1] Includes amounts recorded in current derivative assets of $5 million and $4 million as of June 30, 2025 and December 31, 2024, respectively, and amounts recorded in noncurrent derivative assets of $28 million and $44 million as of June 30, 2025 and December 31, 2024, respectively.