Significant Accounting Policies (Details 2) (Indemnity)	12 Months Ended
Dec. 31, 2011
Indemnity
Recognition of management fee revenue
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange	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