Indemnity Supplemental Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended		12 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		3 Months Ended		6 Months Ended		12 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Jun. 30, 2011 Indemnity	Jun. 30, 2010 Indemnity	Jun. 30, 2011 Indemnity	Jun. 30, 2010 Indemnity	Dec. 31, 2010 Indemnity	Jun. 30, 2010 Indemnity Property and casualty insurance operations	Jun. 30, 2010 Indemnity Property and casualty insurance operations	Mar. 31, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Jun. 30, 2011 Indemnity Management operations	Jun. 30, 2010 Indemnity Management operations	Jun. 30, 2011 Indemnity Management operations	Jun. 30, 2010 Indemnity Management operations	Jun. 30, 2010 Indemnity Life insurance operations	Jun. 30, 2011 Indemnity Life insurance operations	Jun. 30, 2010 Indemnity Life insurance operations	Jun. 30, 2011 Indemnity Investment operations	Jun. 30, 2010 Indemnity Investment operations	Jun. 30, 2011 Indemnity Investment operations	Jun. 30, 2010 Indemnity Investment operations	Jun. 30, 2011 Exchange	Jun. 30, 2010 Exchange	Jun. 30, 2011 Exchange	Jun. 30, 2010 Exchange	Dec. 31, 2010 Exchange	Mar. 31, 2011 Exchange Erie Family Life Insurance Company ("EFL")	Jun. 30, 2011 Exchange Life insurance operations	Jun. 30, 2011 Erie Family Life Insurance Company ("EFL")	Jun. 30, 2010 Erie Family Life Insurance Company ("EFL")	Jun. 30, 2011 Erie Family Life Insurance Company ("EFL")	Jun. 30, 2010 Erie Family Life Insurance Company ("EFL")
Condensed financial statements
Management fee revenue, net														$ 285	$ 270	$ 536	$ 507
Service agreement revenue	8	9	17	17										9	9	17	17
Total revenues	1,245	916	2,610	2,132										294	279	553	524	9	10	18
Cost of management operations														230	217	441	409
Income (loss) from operations before income taxes and noncontrolling interests	(174)	(51)	238	177		81	74	148	141		(2)	(4)		64	62	112	115	3	3	5	17	11	33	25								12	11	25	21
Net premiums earned	1,047	989	2,077	1,967							53	106
Losses and loss expenses	1,170	737	1,876	1,498							40	80
Policy acquisition and underwriting expenses	249	230	496	457							15	30
Total benefits and expenses	1,419	967	2,372	1,955														6	7	13
Net investment income	113	108	218	212		4	9	8	18												4	9	8	18	109	99	210	194
Net realized gains (losses) on investments	39	(213)	188	(88)		6	(3)	7	2												6	(3)	7	2	33	(210)	181	(90)
Net impairment losses recognized in earnings	0	(4)	0	(6)		0	(1)	0	(1)												0	(1)	0	(1)	0	(3)	0	(5)
Equity in earnings of limited partnerships	38	27	110	30																	7	6	18	6
Provision for income taxes	(67)	(20)	71	46		29	25	52	45
Net income	$ (107)	$ (31)	$ 167	$ 131	$ 660	$ 52	$ 49	$ 96	$ 96	$ 162																	$ 71		$ 498
Percent Income attributable to Indemnity shareholder interest (as a percent)											5.50%	5.50%		100.00%	100.00%	100.00%	100.00%	21.60%	21.60%	21.60%
Indemnity's ownership interest in EFL prior to and through March 31, 2011 (as a percent)													21.60%
Exchange's ownership interest in EFL prior to and through March 31, 2011 (as a percent)																														78.40%
Indemnity's ownership interest in EFL sold to the Exchange (as a percent)													21.60%
Exchange's ownership interest in EFL after March 31, 2011 (as a percent)																															100.00%