Related-Party Transactions Schedule of Expenses Incurred By Holdings From Services Provided By Affiliated Company (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transactions [Abstract]
Expenses incurred	$ 204	$ 204	$ 133

Expenses Incurred By Company From Services Provided By Affiliates

No definition available.

Name:	cik0000914748_ExpensesIncurredByCompanyFromServicesProvidedByAffiliates
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration