Postretirement Benefits - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
Employee pension plan
Postretirement Benefits
Funding target (as a percentage of the funding target liability)	100.00%
Defined benefit plan, plan assets, contributions by employer	$ 33
Erie Insurance Exchange | Employee pension plan
Postretirement Benefits
Postretirement annual benefit income and expense reimbursed to and from, respectively, the Exchange and its subsidiaries (as a percent)	61.00%
Erie Insurance Exchange | Supplemental employee retirement plan (SERP)
Postretirement Benefits
Postretirement annual benefit income and expense reimbursed to and from, respectively, the Exchange and its subsidiaries (as a percent)	34.00%