Segment Information - Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting [Line Items]
Total operating revenue	$ 1,089,796		$ 1,060,097		$ 2,101,707	$ 2,049,496
Total operating expenses	885,673		860,924		1,730,797	1,698,947
Operating income	204,123		199,173		370,910	350,549
Total investment income	22,553		19,600		44,672	39,136
Other income	1,401		1,974		2,821	5,808
Income tax expense	47,783		46,062		87,635	82,391
Net income	180,294	$ 150,474	174,685	$ 138,417	$ 330,768	$ 313,102
Erie Insurance Exchange
Segment Reporting [Line Items]
Depreciation and amortization expense reimbursed from the Exchange and its insurance subsidiaries (as a percent)					33.00%	29.00%
Management Operations
Segment Reporting [Line Items]
Total operating revenue	1,089,796		1,060,097		$ 2,101,707	$ 2,049,496
Commissions	508,097		463,442		972,953	900,302
Personnel costs	88,809		85,789		180,872	175,778
Sales and advertising	8,061		9,729		12,966	16,681
Acquisition and underwriting support costs	23,968		27,838		48,092	53,841
Technology infrastructure costs	25,086		24,311		50,889	50,382
Professional fees	19,191		24,192		38,512	50,468
Administrative and other	10,907		12,979		24,863	28,578
Total operating expenses	885,673		860,924		1,730,797	1,698,947
Operating income	204,123		199,173		370,910	350,549
Total investment income	22,553		19,600		44,672	39,136
Other income	1,401		1,974		2,821	5,808
Income tax expense	47,783		46,062		87,635	82,391
Net income	180,294		174,685		330,768	313,102
Depreciation and amortization expense	20,800		16,100		40,800	31,900
Management fee revenue | Management Operations
Segment Reporting [Line Items]
Total operating revenue	882,498		842,149		1,688,372	1,614,843
Administrative services reimbursement revenue
Segment Reporting [Line Items]
Total operating revenue	201,554		212,644		401,650	422,917
Total operating expenses	201,554		212,644		401,650	422,917
Administrative services reimbursement revenue | Management Operations
Segment Reporting [Line Items]
Total operating revenue	201,554		212,644		401,650	422,917
Total operating expenses	201,554		212,644		401,650	422,917
Service agreement revenue
Segment Reporting [Line Items]
Total operating revenue	5,744		5,304		11,685	11,736
Service agreement revenue | Management Operations
Segment Reporting [Line Items]
Total operating revenue	5,744		5,304		11,685	11,736
Cost of operations - policy issuance and renewal services
Segment Reporting [Line Items]
Total operating revenue	862,879		823,853		1,649,278	1,578,902
Total operating expenses	684,119		648,280		1,329,147	1,276,030
Cost of operations - policy issuance and renewal services | Management Operations
Segment Reporting [Line Items]
Total operating expenses	$ 684,119		$ 648,280		$ 1,329,147	$ 1,276,030