Represents the period of prior year actual underwriting data used to estimate agent bonuses.

No definition available.

Name:	erie_AgentBonusEstimateActualUnderwritingDataPeriod
Namespace Prefix:	erie_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the period over which performance is measured for the estimation of agent bonuses.

+ References

No definition available.

+ Details

Name:	erie_AgentBonusPerformancePeriod
Namespace Prefix:	erie_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum maturity period at date of purchase for an available-for-sale security to be considered a current asset.

+ References

No definition available.

+ Details

Name:	erie_AvailableforSaleSecuritiesMaximumMaturity
Namespace Prefix:	erie_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum maturity period at date of purchase for an investment to be considered a cash equivalent.

+ References

No definition available.

+ Details

Name:	erie_CashEquivalentsMaximumMaturity
Namespace Prefix:	erie_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the management fee rate, determined by the board of directors of the entity, calculated as a percentage of the direct and affiliated assumed written premiums.

+ References

No definition available.

+ Details

Name:	erie_InsuranceAgencyManagementFeePercent
Namespace Prefix:	erie_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the Company's number of operating revenue streams based on revenue recognition guidance.

+ References

No definition available.

+ Details

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

- Definition

Property Plant And Equipment and Finite-Lived Intangible Assets, Net By Type [Abstract]

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=erie_ErieInsuranceExchangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	erie_PropertyPlantandEquipmentandFiniteLivedIntangibleAssetsNetByTypeAxis=us-gaap_SoftwareAndSoftwareDevelopmentCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	erie_PropertyPlantandEquipmentandFiniteLivedIntangibleAssetsNetByTypeAxis=erie_VehiclesAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	erie_PropertyPlantandEquipmentandFiniteLivedIntangibleAssetsNetByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	erie_ScheduleOfEquityMethodInvestmentEquityMethodOwnershipPercentAxis=erie_EquityMethodInvestmentOwnershipPercentLessThan10PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Significant Accounting Policies (Details 2)	12 Months Ended
Significant Accounting Policies (Details 2)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue recognition
Number of operating revenue streams	2
Cash and cash equivalents
Cash and cash equivalents, maximum maturity at the date of purchase (in months)	3 months
Available-for-sale securities
Available-for-sale securities, maximum maturity to be classified as current assets (in months)	12 months
Agent bonus estimates
Performance period for agent bonuses (in months)	36 months
Period of prior year actual underwriting data used to estimate agent bonuses (in years)	2 years
Erie Insurance Exchange (EIE)
Recognition of management fee revenue
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)	25.00%	25.00%	25.00%
Maximum \| Erie Insurance Exchange (EIE)
Recognition of management fee revenue
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)	25.00%
Software \| Minimum
Fixed assets
Estimated useful life (in years)	3 years
Software \| Maximum
Fixed assets
Estimated useful life (in years)	7 years
Equipment \| Minimum
Fixed assets
Estimated useful life (in years)	3 years
Equipment \| Maximum
Fixed assets
Estimated useful life (in years)	10 years
Buildings and building improvements \| Minimum
Fixed assets
Estimated useful life (in years)	20 years
Buildings and building improvements \| Maximum
Fixed assets
Estimated useful life (in years)	45 years
Less than 10%
Limited partnerships
Limited partnerships, general ownership percentage (as a percent)	10.00%