Indemnity Supplemental Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Indemnity	Jun. 30, 2011 Indemnity	Jun. 30, 2012 Indemnity	Jun. 30, 2011 Indemnity	Jun. 30, 2012 Indemnity Management operations	Jun. 30, 2011 Indemnity Management operations	Jun. 30, 2012 Indemnity Management operations	Jun. 30, 2011 Indemnity Management operations	Jun. 30, 2011 Indemnity Life insurance operations	Mar. 31, 2011 Indemnity Life insurance operations	Jun. 30, 2012 Indemnity Investment operations	Jun. 30, 2011 Indemnity Investment operations	Jun. 30, 2012 Indemnity Investment operations	Jun. 30, 2011 Indemnity Investment operations	Mar. 31, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Jun. 30, 2012 Exchange	Jun. 30, 2011 Exchange	Jun. 30, 2012 Exchange	Jun. 30, 2011 Exchange	Mar. 31, 2011 Exchange Erie Family Life Insurance Company ("EFL")
Condensed financial statements
Management fee revenue, net									$ 308	$ 285	$ 577	$ 536
Service agreement revenue	8	8	16	17					8	9	15	17
Total revenues	1,160	1,245	2,680	2,610					316	294	592	553	10
Cost of management operations									257	230	487	441
Total benefits and expenses	1,230	1,419	2,216	2,372									7
Net investment income	113	113	221	218	4	4	8	8							4	4	8	8		109	109	213	210
Net realized investment (losses) gains	(107)	39	189	188	(1)	6	2	7							(1)	6	2	7		(106)	33	187	181
Net impairment losses recognized in earnings	0	0	0	0											0	0	0	0				(0.1)
Equity in earnings of limited partnerships	37	38	58	110											3	7	4	18
(Loss) income from operations before income taxes and noncontrolling interest	(70)	(174)	464	238	65	81	119	148	59	64	105	112	3		6	17	14	33
Provision for income taxes	(32)	(67)	148	71	22	29	40	52
Net income	$ 43	$ 52	$ 79	$ 96	$ 43	$ 52	$ 79	$ 96
Percent income attributable to Indemnity shareholder interest									100.00%	100.00%	100.00%	100.00%		21.60%
Indemnity's ownership interest in EFL prior to and through March 31, 2011 (as a percent)																			21.60%
Indemnity's ownership interest in EFL sold to the Exchange (as a percent)																			21.60%
Exchange's ownership interest in EFL prior to and through March 31, 2011 (as a percent)																								78.40%
Exchange's ownership interest in EFL after March 31, 2011 (as a percent)																								100.00%