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

No definition available.

Name:	erie_EquitySecuritiesFVNIGainLossAlternativeAbstract
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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

No definition available.

Name:	erie_EquitySecuritiesFVNIRealizedGainLoss
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Data Type:	xbrli:monetaryItemType
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Amount of unrealized 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_EquitySecuritiesFVNIUnrealizedGainLoss
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Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings.

No definition available.

Name:	erie_OtherthantemporaryImpairmentLossDebtSecuritiesAvailableforsaleRecognizedinEarnings
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Data Type:	xbrli:monetaryItemType
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- References

No definition available.

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecuritiesAbstract
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Data Type:	xbrli:stringItemType
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Amount before tax of other than temporary impairment (OTTI) on investment in available-for-sale debt security, recognized in other comprehensive loss.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e25362-111560

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580