Related-Party Transactions (Expenses Incurred By Holdings From Services Provided By Affiliated Company) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Related-Party Transactions [Abstract]
Expenses incurred	$ 21,242	$ 20,359	$ 62,701	$ 58,555

Expenses incurred by holdings from services provided by affiliates

No definition available.

Name:	cik0000914748_ExpensesIncurredByHoldingsFromServicesProvidedByAffiliates
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration