Significant Accounting Policies (Details)	6 Months Ended
Jun. 30, 2017
Revenue recognition
Number of operating revenue streams	2

Represents the Company's number of operating revenue streams based on revenue recognition guidance.

No definition available.

Name:	erie_NumberOfRevenueStreams
Namespace Prefix:	erie_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration