Related-Party Transactions (Expenses Incurred By Holdings From Services Provided By Affiliated Company) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Related-Party Transactions [Abstract]
Expenses incurred	$ 20,700	$ 16,537	$ 57,073	$ 46,984

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