Observable Input, Constant Maturity Term

No definition available.

Name:	cik0000914748_ObservableInputConstantMaturityTerm
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Preferred Stock Term

+ References

No definition available.

+ Details

Name:	cik0000914748_PreferredStockTerm
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Public equity portfolio fair value disclosure.

+ References

No definition available.

+ Details

Name:	cik0000914748_PublicEquityPortfolioFairValueDisclosure
Namespace Prefix:	cik0000914748_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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

- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value portion of other assets.

+ References

No definition available.

+ Details

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

- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

+ Details

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_FixedMaturitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=cik0000914748_InvestmentManagersValuationCommitteesValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=cik0000914748_NonBindingBrokerQuoteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_RedeemableConvertiblePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_NewAccountingPronouncementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cik0000914748_SeniorNotes4868Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Fair Value (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
Fair Value (Narrative) (Details) - USD ($)	Dec. 31, 2015	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of public equity portfolio		$ 155,784,000		$ 155,784,000		$ 124,228,000
Annual dividend rate	1.75%
Transfers between Level 1 and Level 2		0		0
Investments within other invested assets		1,892,988,000		1,892,988,000		1,717,336,000
Transfers from level 3		3,977,000		1,519,000
Market Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers from level 3		3,977,000	$ 1,750,000	1,519,000	$ 1,750,000
Market Value [Member] \| Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		474,322,000		474,322,000		383,994,000
Market Value [Member] \| Fixed Maturities [Member] \| Investment Managers' Valuation Committees, Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		412,095,000		412,095,000		354,133,000
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers from level 3
Fair Value [Member] \| Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities						2,337,000
Fair Value [Member] \| Fixed Maturities [Member] \| Investment Managers' Valuation Committees, Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities						2,337,000
Fair Value [Member] \| Fixed Maturities [Member] \| Non-Binding Broker Quote [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities						1,153,000
Redeemable Convertible Preferred Stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Preferred stock tern				25 years
Annual dividend rate				1.75%
Adjustments for New Accounting Pronouncement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments within other invested assets		154,908,000		$ 154,908,000		117,662,000
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments within other invested assets
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments within other invested assets		1,892,988,000		1,892,988,000		1,717,336,000
Fair Value, Inputs, Level 3 [Member] \| Fair Value [Member] \| Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		$ 62,228,000		$ 62,228,000		$ 28,708,000
Senior Notes [Member] \| Senior Notes 4.868% [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Observable input constant maturity				20 years
Debt instrument, stated interest rate		4.868%		4.868%
Date Due				Jun. 01, 2044		Jun. 01, 2044