Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cost of pension plans:
Service cost for benefits earned	$ 12,560	$ 13,260
Interest cost on benefits obligation	9,941	9,206
Expected return on plan assets	(13,639)	(12,569)
Prior service cost amortization	361	357
Net actuarial loss amortization	1,830	4,027
Pension plan cost	$ 11,053	$ 14,281
Erie Insurance Exchange
Postretirement Benefits
Postretirement annual benefit expense reimbursed to Indemnity from the Exchange and its subsidiaries (as a percent)	58.00%