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

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), excluding other-than-temporary impairment (OTTI).

No definition available.

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

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), excluding other-than-temporary impairment (OTTI).

No definition available.

Name:	erie_DebtSecuritiesAvailableforsaleRealizedLossExcludingOtherthantemporaryImpairment
Namespace Prefix:	erie_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

No definition available.

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

Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]

No definition available.

Name:	erie_EquitySecuritiesFVNIGainLossAlternativeAbstract
Namespace Prefix:	erie_
Data Type:	xbrli:stringItemType
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- References

No definition available.

Name:	us-gaap_AvailableforsaleSecuritiesGrossRealizedGainLossExcludingOtherThanTemporaryImpairmentsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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Period Type:	duration

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (b)(7)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20187-122688

Name:	us-gaap_GainLossOnInvestmentsExcludingOtherThanTemporaryImpairments
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- References

No definition available.

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

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 325
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031664&loc=d3e22529-158502

Name:	us-gaap_RealizedInvestmentGainsLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- References

No definition available.