The number of employer shares or related party shares included in the defined contribution plan assets.

No definition available.

Name:	erie_DefinedContributionPlanNumberOfEquitySecuritiesIssuedByEmployerAndRelatedPartiesIncludedInPlanAssets
Namespace Prefix:	erie_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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Postretirement Benefits (Details 12) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee savings plan
Employer matching contribution paid to the plan	$ 11	$ 10	$ 9
Class A common stock held by plan participants (in shares)	0.2	0.2
100% employer matching contribution
Employee savings plan
Percentage of employer matching contribution of employee contributions (as a percent)	100.00%
100% employer matching contribution \| Maximum
Employee savings plan
Percentage of eligible employee compensation, matched by employer (as a percent)	3.00%
50% employer matching contribution
Employee savings plan
Percentage of employer matching contribution of employee contributions (as a percent)	50.00%
50% employer matching contribution \| Maximum
Employee savings plan
Percentage of eligible employee compensation, matched by employer (as a percent)	5.00%
50% employer matching contribution \| Minimum
Employee savings plan
Percentage of eligible employee compensation, matched by employer (as a percent)	3.00%