Leases (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use asset, statement of financial position	us-gaap:OtherAssetsNoncurrent		us-gaap:OtherAssetsNoncurrent
Operating lease, liability, current, statement of financial position	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent		us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Operating lease, liability, noncurrent, statement of financial position	us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent
Operating lease costs	$ 3,200	$ 3,500	$ 9,900	$ 10,700
Erie Insurance Exchange
Lessee, Lease, Description [Line Items]
Operating lease costs, amount reimbursed from Exchange and its subsidiaries	1,300	$ 1,500	4,100	$ 4,600
Erie Insurance Exchange | Office Space
Lessee, Lease, Description [Line Items]
Operating lease assets	7,800		7,800
Operating lease assets
Lessee, Lease, Description [Line Items]
Operating lease assets	16,844		16,844		$ 22,401
Operating lease liabilities - current
Lessee, Lease, Description [Line Items]
Operating lease liabilities - current	10,735		10,735		11,289
Operating lease liabilities - long-term
Lessee, Lease, Description [Line Items]
Operating lease liabilities - long-term	5,766		5,766		10,665
Operating lease liabilities
Lessee, Lease, Description [Line Items]
Total operating lease liabilities	$ 16,501		$ 16,501		$ 21,954