Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Premiums earned/life policy revenue									$ 5,344	$ 4,898	$ 4,493
Net investment income									446	422	438
Net realized investment gains (losses)									193	771	418
Net impairment losses recognized in earnings									(4)	(13)	0
Equity in earnings of limited partnerships									113	161	131
Service agreement and other revenue									32	32	32
Total revenues	1,589	1,426	1,598	1,511	1,697	1,577	1,426	1,571	6,124	6,271	5,512
Benefits and expenses
Insurance losses and loss expenses									3,958	3,467	3,480
Policy acquisition and underwriting expenses									1,336	1,237	1,133
Total benefits and expenses	1,212	1,276	1,451	1,355	1,227	1,179	1,163	1,135	5,294	4,704	4,613
Income (loss) from operations before income taxes and noncontrolling interest	377	150	147	156	470	398	263	436	830	1,567	899
Provision for income taxes									257	519	280
Net income (loss)	253	108	103	109	314	267	177	290	573	1,048	619
Indemnity
Revenues
Net investment income									16	15	16
Net realized investment gains (losses)									1	1	5
Net impairment losses recognized in earnings									0	0	0
Equity in earnings of limited partnerships									11	22	15
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest									251	247	241
Provision for income taxes									83	84	81
Exchange
Revenues
Net investment income									430	407	422
Net realized investment gains (losses)									192	770	413
Net impairment losses recognized in earnings									(4)	(13)	0
Equity in earnings of limited partnerships									102	139	116
Benefits and expenses
Provision for income taxes									174	435	199
Management operations | Indemnity
Segment information
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)									25.00%
Revenues
Management fee revenue									1,376	1,266	1,157
Service agreement and other revenue									31	31	31
Total revenues									1,407	1,297	1,188
Benefits and expenses
Cost of management operations									1,184	1,088	983
Income (loss) from operations before income taxes and noncontrolling interest									223	209	205
Investment operations | Indemnity
Revenues
Net investment income									16	15	16
Net realized investment gains (losses)									1	1	5
Net impairment losses recognized in earnings									0	0	0
Equity in earnings of limited partnerships									11	22	15
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest									28	38	36
Operating segment | Management operations
Segment information
Reduction in commission expense due to adjustment											6
Indemnity commission expense adjustment description									This amount represents the reimbursement by the North Carolina Reinsurance Facility (NCRF) for commissions Indemnity paid to agents on the surcharges collected on behalf of the NCRF which was incorrectly recorded as a benefit to the Exchange in prior periods.
Revenues
Management fee revenue									1,376	1,266	1,157
Service agreement and other revenue									31	31	31
Total revenues									1,407	1,297	1,188
Benefits and expenses
Cost of management operations									1,184	1,088	983
Total benefits and expenses									1,184	1,088	983
Income (loss) from operations before income taxes and noncontrolling interest									223	209	205
Provision for income taxes									78	73	72
Net income (loss)									145	136	133
Operating segment | Management operations | Indemnity
Segment information
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)									25.00%
Operating segment | Property and casualty insurance operations
Revenues
Premiums earned/life policy revenue									5,260	4,820	4,422
Total revenues									5,260	4,820	4,422
Benefits and expenses
Insurance losses and loss expenses									3,859	3,365	3,384
Policy acquisition and underwriting expenses									1,502	1,387	1,284
Total benefits and expenses									5,361	4,752	4,668
Income (loss) from operations before income taxes and noncontrolling interest									(101)	68	(246)
Provision for income taxes									(35)	24	(86)
Net income (loss)									(66)	44	(160)
Operating segment | Life insurance operations
Revenues
Premiums earned/life policy revenue									86	80	73
Service agreement and other revenue									1	1	1
Total revenues									87	81	74
Benefits and expenses
Insurance losses and loss expenses									105	107	101
Policy acquisition and underwriting expenses									38	37	31
Total benefits and expenses									143	144	132
Income (loss) from operations before income taxes and noncontrolling interest									(56)	(63)	(58)
Provision for income taxes									(20)	(22)	(20)
Net income (loss)									(36)	(41)	(38)
Operating segment | Life insurance operations | Erie Family Life Insurance Company (EFL)
Segment information
Total investment revenues									105	111	104
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest									49	48	46
Operating segment | Investment operations
Revenues
Net investment income									462	434	449
Net realized investment gains (losses)									193	771	418
Net impairment losses recognized in earnings									(4)	(13)	0
Equity in earnings of limited partnerships									113	161	131
Total revenues									764	1,353	998
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest									764	1,353	998
Provision for income taxes									234	444	314
Net income (loss)									530	909	684
Eliminations
Revenues
Premiums earned/life policy revenue									(2)	(2)	(2)
Net investment income									(16)	(12)	(11)
Management fee revenue									(1,376)	(1,266)	(1,157)
Total revenues									(1,394)	(1,280)	(1,170)
Benefits and expenses
Cost of management operations									(1,184)	(1,088)	(983)
Insurance losses and loss expenses									(6)	(5)	(5)
Policy acquisition and underwriting expenses									(204)	(187)	(182)
Total benefits and expenses									$ (1,394)	$ (1,280)	$ (1,170)