Income Taxes (Details)	6 Months Ended
Jun. 30, 2016
Income taxes
Effective tax rate when investment related permanent tax differences are excluded (as a percent)	35.00%
Minimum
Income taxes
Percent of total permanent tax differences related to investment revenues (as a percent)	98.00%

Represents the effective tax rate if permanent tax differences related to investment revenues were excluded from the calculation (such as tax exempt interest and dividends received deduction).

No definition available.

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