Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cost of pension plans:
Service cost for benefits earned	$ 13,260	$ 10,874	$ 26,520	$ 21,747
Interest cost on benefits obligation	9,206	9,394	18,412	18,789
Expected return on plan assets	(12,568)	(12,353)	(25,137)	(24,706)
Prior service cost amortization	357	335	714	671
Net actuarial loss amortization	4,026	3,031	8,053	6,062
Pension plan cost	$ 14,281	$ 11,281	$ 28,562	$ 22,563
Erie Insurance Exchange
Postretirement Benefits
Postretirement annual benefit expense reimbursed to Indemnity from the Exchange and its subsidiaries (as a percent)			58.00%