Asset Retirement Obligations (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation, other conditional obligations	$ 420	$ 329
Asset retirement obligation, nuclear decommissioning	$ 311	$ 299

Asset Retirement Obligation Other Conditional Obligations

No definition available.

Name:	ck0000091882_AssetRetirementObligationOtherConditionalObligations
Namespace Prefix:	ck0000091882_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant