Related-Party Transactions (Dividends Received On Common Shares Reported As Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Dividends From Parent's Shares [Member]
Related Party Transaction [Line Items]
Dividends received		$ 9,234
Dividends From Preferred Shares Of Affiliate [Member]
Related Party Transaction [Line Items]
Dividends received	$ 7,758

Dividends received on common shares, reported as net investment income in consolidated statements of operations and comprehensive income (loss).

No definition available.

Name:	cik0000914748_DividendsReceivedOnCommonSharesReportedAsNetInvestmentIncomeInConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration