Variable Interest Entity (Details) (Indemnity)	3 Months Ended
Mar. 31, 2013
Indemnity
Variable Interest Entity disclosures
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)	25.00%

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