Concentrations of Credit Risk (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Concentrations of credit risk from unsecured receivables
Receivables from Erie Insurance Exchange and its subsidiaries	$ 463,620	$ 418,328

Amount of receivables arising from transactions with related parties due within one year or the normal operating cycle, if longer.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant