Related-Party Transactions (Expenses Incurred By Holdings From Services Provided By Affiliated Company) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Related-Party Transactions [Abstract]
Expenses incurred	$ 18,363	$ 15,843

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