Revenue - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Obligations	Jun. 30, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Indemnity's management fee rate as a percent of direct and affiliated assumed written premiums of the Exchange (percentage)				25.00%
Performance obligations under subscriber's agreement \| Obligations				2
Increase in allowance for cancellations \| $	$ 0.9	$ 3.5	$ 2.0	$ 4.4	$ 2.9

Change in the estimated allowance to reduce the management fee to its estimated net realizable value to account for the potential of mid-term policy cancellations based on historical cancellation rates.

No definition available.

Name:	erie_RevenueRecognitionManagementFeeReturnedPremiumCancellationAllowance
Namespace Prefix:	erie_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration