Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Revenues
Premiums earned/life policy revenue	$ 1,215	$ 1,109	$ 2,390	$ 2,196
Net investment income	104	113	207	221
Net realized investment gains (losses)	61	(107)	310	189
Net impairment losses recognized in earnings	(1.0)	0	(1.0)	0
Equity in earnings of limited partnerships	39	37	75	58
Service agreement and other revenue	8	8	16	16
Total revenues	1,426	1,160	2,997	2,680
Benefits and expenses
Insurance losses and loss expenses	861	943	1,703	1,659
Policy acquisition and underwriting expenses	302	287	595	557
Total benefits and expenses	1,163	1,230	2,298	2,216
Income (loss) from operations before income taxes and noncontrolling interest	263	(70)	699	464
Provision for income taxes	86	(32)	232	148
Net income (loss)	177	(38)	467	316	619
Management operations
Segment information
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)			25.00%
Reduction in commission expense due to adjustment		6		6
Indemnity commission expense adjustment			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	336	308	632	577
Service agreement and other revenue	8	8	15	15
Total revenues	344	316	647	592
Benefits and expenses
Cost of management operations	285	257	539	487
Total benefits and expenses	285	257	539	487
Income (loss) from operations before income taxes and noncontrolling interest	59	59	108	105
Provision for income taxes	21	21	38	37
Net income (loss)	38	38	70	68
Property and casualty insurance operations
Revenues
Premiums earned/life policy revenue	1,196	1,092	2,352	2,161
Total revenues	1,196	1,092	2,352	2,161
Benefits and expenses
Insurance losses and loss expenses	837	919	1,654	1,611
Policy acquisition and underwriting expenses	348	332	676	634
Total benefits and expenses	1,185	1,251	2,330	2,245
Income (loss) from operations before income taxes and noncontrolling interest	11	(159)	22	(84)
Provision for income taxes	4	(55)	8	(29)
Net income (loss)	7	(104)	14	(55)
Life insurance operations
Revenues
Premiums earned/life policy revenue	20	18	39	36
Service agreement and other revenue	0	0	1	1
Total revenues	20	18	40	37
Benefits and expenses
Insurance losses and loss expenses	26	25	52	50
Policy acquisition and underwriting expenses	7	8	16	17
Total benefits and expenses	33	33	68	67
Income (loss) from operations before income taxes and noncontrolling interest	(13)	(15)	(28)	(30)
Provision for income taxes	(5)	(6)	(10)	(11)
Net income (loss)	(8)	(9)	(18)	(19)
Investment operations
Revenues
Net investment income	107	115	213	226
Net realized investment gains (losses)	61	(107)	310	189
Net impairment losses recognized in earnings	(1.0)	0	(1.0)	0
Equity in earnings of limited partnerships	39	37	75	58
Total revenues	206	45	597	473
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	206	45	597	473
Provision for income taxes	66	8	196	151
Net income (loss)	140	37	401	322
Eliminations
Revenues
Premiums earned/life policy revenue	(1)	(1)	(1)	(1)
Net investment income	(3)	(2)	(6)	(5)
Management fee revenue	(336)	(308)	(632)	(577)
Total revenues	(340)	(311)	(639)	(583)
Benefits and expenses
Cost of management operations	(285)	(257)	(539)	(487)
Insurance losses and loss expenses	(2)	(1)	(3)	(2)
Policy acquisition and underwriting expenses	(53)	(53)	(97)	(94)
Total benefits and expenses	(340)	(311)	(639)	(583)
Erie Family Life Insurance Company ("EFL") | Life insurance operations
Segment information
Total investment revenues	26	28	52	52
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	$ 13	$ 13	$ 24	$ 22