Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Total operating revenue	$ 1,066,739			$ 999,886			$ 3,116,235	$ 2,871,025
Total operating expenses	857,818			819,761			2,556,765	2,361,880
Operating income	208,921			180,125			559,470	509,145
Total investment income	21,554			19,549			60,690	48,455
Other income	2,286			1,168			8,094	7,871
Income tax expense	49,908			41,012			132,299	117,186
Net income	182,853	$ 174,685	$ 138,417	159,830	$ 163,903	$ 124,552	$ 495,955	$ 448,285
Erie Insurance Exchange
Segment Reporting Information [Line Items]
Depreciation and amortization expense reimbursed from the Exchange and its insurance subsidiaries (as a percent)							30.00%	28.00%
Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	1,066,739			999,886			$ 3,116,235	$ 2,871,025
Commissions	461,513			420,516			1,361,815	1,216,227
Underwriting and policy processing	53,097			51,449			156,264	150,350
Information technology	56,294			54,825			178,748	158,914
Sales and advertising	14,342			18,725			51,498	52,886
Customer service	12,176			11,300			35,253	31,726
Administrative and other	44,702			56,192			134,576	147,428
Total operating expenses	857,818			819,761			2,556,765	2,361,880
Operating income	208,921			180,125			559,470	509,145
Total investment income	21,554			19,549			60,690	48,455
Other income	2,286			1,168			8,094	7,871
Income tax expense	49,908			41,012			132,299	117,186
Net income	182,853			159,830			495,955	448,285
Depreciation and amortization expense	18,400			14,400			50,300	41,500
Management fee revenue | Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	844,106			786,316			2,458,949	2,246,873
Administrative services reimbursement revenue
Segment Reporting Information [Line Items]
Total operating revenue	215,694			206,754			638,611	604,349
Total operating expenses	215,694			206,754			638,611	604,349
Administrative services reimbursement revenue | Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	215,694			206,754			638,611	604,349
Total operating expenses	215,694			206,754			638,611	604,349
Service agreement revenue
Segment Reporting Information [Line Items]
Total operating revenue	6,939			6,816			18,675	19,803
Service agreement revenue | Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	6,939			6,816			18,675	19,803
Cost of operations - policy issuance and renewal services
Segment Reporting Information [Line Items]
Total operating revenue	825,275			769,162			2,404,177	2,195,734
Total operating expenses	642,124			613,007			1,918,154	1,757,531
Cost of operations - policy issuance and renewal services | Management Operations
Segment Reporting Information [Line Items]
Total operating expenses	$ 642,124			$ 613,007			$ 1,918,154	$ 1,757,531