Name:	erie_FairValueAssetsLevel1ToLevel2TransfersAmountDuringPeriod
Namespace Prefix:	erie_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1 which have taken place during the period.

No definition available.

Name:	erie_FairValueAssetsLevel2ToLevel1TransfersAmountDuringPeriod
Namespace Prefix:	erie_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 3 which have taken place during the period.

No definition available.

Name:	erie_FairValueAssetsLevel2ToLevel3TransfersAmountDuringPeriod
Namespace Prefix:	erie_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of transfers of assets measured on a recurring basis out of Level 3 of the fair value hierarchy into Level 2 which have taken place during the period.

No definition available.

Name:	erie_FairValueAssetsLevel3ToLevel2TransfersAmountDuringPeriod
Namespace Prefix:	erie_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

-- None. No documentation exists for this element. --

No definition available.

Name:	erie_FairValueTransfersDueToChangesInAvailableMarketObservableInputsAbstract
Namespace Prefix:	erie_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the number of securities in the entity's investment portfolio that necessitated reclassification between Level 2 and Level 3 due to trading activity levels.

No definition available.

Name:	erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel2AndLevel3
Namespace Prefix:	erie_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of securities in the entity's investment portfolio that necessitated reclassification between Level 3 and Level 2 due to trading activity levels.

No definition available.

Name:	erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel3AndLevel2
Namespace Prefix:	erie_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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

Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

No definition available.

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

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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

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

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

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_AvailableforsaleSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

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