Variable Interest Entity (Details) (Indemnity)	9 Months Ended
Sep. 30, 2012	Mar. 31, 2011 Erie Family Life Insurance Company ("EFL")
Variable Interest Entity disclosures
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange	25.00%
Indemnity's ownership interest in EFL sold to the Exchange (as a percent)		21.60%

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

No definition available.

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