Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Jan. 31, 2026	Jun. 30, 2026	Sep. 30, 2026
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	$ 47
Employee pension plan | Forecast
Postretirement Benefits
Defined benefit plan, expected future employer contributions, remainder of fiscal year			$ 30
Erie Insurance Exchange | Employee pension plan
Postretirement Benefits
Postretirement annual benefit expense reimbursed from the Exchange and its insurance subsidiaries (as a percent)		61.00%
Erie Insurance Exchange | Supplemental employee retirement plan (SERP)
Postretirement Benefits
Postretirement annual benefit expense reimbursed from the Exchange and its insurance subsidiaries (as a percent)		33.00%