Indemnity Supplemental Information (Details) (USD $) In Millions, unless otherwise specified												12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011 Erie Family Life Insurance Company ("EFL")	Dec. 31, 2010 Erie Family Life Insurance Company ("EFL")	Dec. 31, 2009 Erie Family Life Insurance Company ("EFL")	Dec. 31, 2011 Indemnity	Dec. 31, 2010 Indemnity	Dec. 31, 2009 Indemnity	Dec. 31, 2008 Indemnity	Dec. 31, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Dec. 31, 2010 Indemnity Erie Family Life Insurance Company ("EFL")	Mar. 31, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Dec. 31, 2011 Exchange	Dec. 31, 2010 Exchange	Dec. 31, 2011 Reclassifications and eliminations	Dec. 31, 2010 Reclassifications and eliminations
Available-for-sale securities, at fair value:
Fixed maturities	$ 7,840	$ 7,543						$ 548	$ 264						$ 7,292	$ 7,279
Equity securities	589	594						25	24						564	570
Trading securities, at fair value	2,335	2,334						27	28						2,308	2,306
Limited partnerships	1,290	1,324						208	216						1,082	1,108
Other invested assets	20	20						1	1						19	19
Total investments	12,074	11,815						809	533						11,265	11,282
Cash and cash equivalents	185	430	234	277				11	310	76	61				174	120
Premiums receivable from policyholders	976	942													976	942
Reinsurance recoverable	166	201													166	201
Deferred income taxes	19							19	0
Deferred acquisition costs	487	467			144	140	154								487	467
Other assets	441	489						119	132						322	357
Receivables from the Exchange and other affiliates								254	232			3	3				(254)	(232)
Note receivable from EFL								25	25								(25)	(25)
Equity in EFL									80									(80)
Total assets	14,348	14,344						1,237	1,312						13,390	13,369	(279)	(337)
Liabilities
Losses and loss expense reserves	3,499	3,584													3,499	3,584
Life policy and deposit contract reserves	1,671	1,603	1,540												1,671	1,603
Unearned premiums	2,178	2,082													2,178	2,082
Deferred income taxes	147	283						0	26						147	257
Other liabilities, prior to consolidation eliminations	560	458						456	374						383	341	(279)	(257)
Total liabilities	8,055	8,010						456	400						7,878	7,867	(279)	(257)
Indemnity's shareholders' equity
Total Indemnity shareholders' equity	781	912						781	912
Noncontrolling interest in consolidated entity - Exchange, prior to consolidation eliminations	5,512	5,422													5,512	5,502		(80)
Total equity, prior to consolidation eliminations	6,293	6,334						781	912						5,512	5,502		(80)
Total liabilities, shareholders' equity and noncontrolling interest	14,348	14,344						1,237	1,312						13,390	13,369	(279)	(337)
Indemnity's ownership interest in EFL sold to the Exchange (as a percent)														21.60%
Note receivable from EFL, annual interest rate (as a percent)												6.70%
EFL annual interest paid to Indemnity												2	2
Receivables from the Exchange								$ 251	$ 229