Investments (Summary Of Components Of Net Investment Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	$ 74,116	$ 66,426
Funds held interest income (expense)	2,521	2,109
Interest income from Parent	1,075cik0000914748_InterestIncomeFromParent
Gross investment income	77,712	68,535
Investment expenses	(5,131)	(4,748)
Net investment income	72,581us-gaap_InvestmentIncomeNet	63,787us-gaap_InvestmentIncomeNet
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	47,972	51,079
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	8,742	8,937
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	164	186
Limited Partnerships [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	7,379	(3,087)
Dividends From Parent's Shares [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	9,234	7,290
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	$ 625	$ 2,021

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Amount of expenses related to the generation of investment income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

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-Name Accounting Standards Codification

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