Significant Accounting Policies (Details 2)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Erie Insurance Exchange (EIE)
Revenue, Performance Obligation [Abstract]
Indemnity's management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)		25.00%	25.00%	25.00%
Scenario, Forecast | Erie Insurance Exchange (EIE)
Revenue, Performance Obligation [Abstract]
Indemnity's management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)	25.00%
Scenario, Forecast | Accounting Standards Update 2014-09
Revenue, Performance Obligation [Abstract]
Number of performance obligations recognized by Indemnity acting as attorney-in-fact for the subscribers of the Exchange	2
Scenario, Forecast | Accounting Standards Update 2014-09 | Erie Insurance Exchange (EIE)
Revenue, Performance Obligation [Abstract]
Indemnity's management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)	25.00%