Segment Information - Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Total operating revenue	$ 1,011,911	$ 989,399
Total operating expenses	845,124	838,023
Operating income	166,787	151,376
Total investment income	22,119	19,536
Other income	1,420	3,834
Income tax expense	39,852	36,329
Net income	$ 150,474	$ 138,417
Erie Insurance Exchange
Segment Reporting Information [Line Items]
Depreciation and amortization expense reimbursed from the Exchange and its insurance subsidiaries (as a percent)	32.00%	29.00%
Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	$ 1,011,911	$ 989,399
Commissions	464,856	436,860
Personnel costs	92,063	89,989
Sales and advertising	4,905	6,952
Acquisition and underwriting support costs	24,124	26,003
Technology infrastructure costs	25,803	26,071
Professional fees	19,321	26,276
Administrative and other	13,956	15,599
Total operating expenses	845,124	838,023
Operating income	166,787	151,376
Total investment income	22,119	19,536
Other income	1,420	3,834
Income tax expense	39,852	36,329
Net income	150,474	138,417
Depreciation and amortization expense	20,000	15,800
Management fee revenue | Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	805,874	772,694
Administrative services reimbursement revenue
Segment Reporting Information [Line Items]
Total operating revenue	200,096	210,273
Total operating expenses	200,096	210,273
Administrative services reimbursement revenue | Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	200,096	210,273
Total operating expenses	200,096	210,273
Service agreement revenue
Segment Reporting Information [Line Items]
Total operating revenue	5,941	6,432
Service agreement revenue | Management Operations
Segment Reporting Information [Line Items]
Total operating revenue	5,941	6,432
Cost of operations - policy issuance and renewal services
Segment Reporting Information [Line Items]
Total operating revenue	786,399	755,049
Total operating expenses	645,028	627,750
Cost of operations - policy issuance and renewal services | Management Operations
Segment Reporting Information [Line Items]
Total operating expenses	$ 645,028	$ 627,750