Junior Subordinated Debt Securities Payable (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Junior subordinated debt securities, maturity date	Mar. 29, 2034
Net assets of Holdings' consolidated subsidiaries, subject to regulatory restrictions		$ 2,108,692
Net assets of consolidated subsidiaries		$ 2,763,171
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Percentage of principal redeemable before maturity	100.00%
Debt securities, Trust may become subject to tax within number of days of redemption period	90 days

Debt Securities Maturity Percentage In Date Of Redemption

No definition available.

Name:	cik0000914748_DebtSecuritiesMaturityPercentageInDateOfRedemption
Namespace Prefix:	cik0000914748_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum Days For Debt Securities Become Subject To Tax

+ References

No definition available.

+ Details

Name:	cik0000914748_MinimumDaysForDebtSecuritiesBecomeSubjectToTax
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of restricted net assets of consolidated and unconsolidated subsidiaries as of the end of the most recently completed fiscal year.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(e)(3)(ii))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph e

-Subparagraph 3

-Article 4

+ Details

Name:	us-gaap_AmountOfRestrictedNetAssetsForConsolidatedAndUnconsolidatedSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date of maturity of a debt security categorized as held-to-maturity, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_HeldtomaturitySecuritiesDebtMaturitiesDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

Name:	us-gaap_NetRegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant