Indemnity Supplemental Information (Details) (USD $) In Millions, unless otherwise specified									3 Months Ended		9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2009	Sep. 30, 2011 Indemnity	Dec. 31, 2010 Indemnity	Sep. 30, 2010 Indemnity	Dec. 31, 2009 Indemnity	Sep. 30, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Sep. 30, 2010 Indemnity Erie Family Life Insurance Company ("EFL")	Sep. 30, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Mar. 31, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Sep. 30, 2011 Exchange	Dec. 31, 2010 Exchange	Sep. 30, 2011 Reclassifications and eliminations	Dec. 31, 2010 Reclassifications and eliminations
Available-for-sale securities, at fair value:
Fixed maturities	$ 7,848	$ 7,543			$ 517	$ 264							$ 7,331	$ 7,279
Equity securities	613	594			22	24							591	570
Trading securities, at fair value	2,111	2,334			26	28							2,085	2,306
Limited partnerships	1,410	1,324			223	216							1,187	1,108
Other invested assets	20	20			1	1							19	19
Total investments	12,002	11,815			789	533							11,213	11,282
Cash and cash equivalents	76	430	312	234	34	310	73	76					42	120
Premiums receivable from policyholders	1,035	942											1,035	942
Reinsurance recoverable	197	201											197	201
Deferred acquisition costs	495	467											495	467
Other assets	458	489			109	132							349	357
Receivables from Exchange and other affiliates					269	232									(269)	(232)
Note receivable from EFL					25	25									(25)	(25)
Equity in EFL						80										(80)
Total assets	14,263	14,344			1,226	1,312							13,331	13,369	(294)	(337)
Liabilities
Losses and loss expense reserves	3,686	3,584											3,686	3,584
Life policy and deposit contract reserves	1,659	1,603											1,659	1,603
Unearned premiums	2,249	2,082											2,249	2,082
Deferred income taxes	103	283			6	26							97	257
Other liabilities	468	458			375	374							387	341	(294)	(257)
Total liabilities	8,165	8,010			381	400							8,078	7,867	(294)	(257)
Indemnity's shareholders' equity
Total Indemnity shareholders' equity	845	912			845	912
Noncontrolling interest in consolidated entity - Exchange	5,253	5,422											5,253	5,502		(80)
Total equity	6,098	6,334			845	912							5,253	5,502		(80)
Total liabilities, shareholders' equity and noncontrolling interest	14,263	14,344			1,226	1,312							13,331	13,369	(294)	(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 accrued interest to Indemnity (in dollars)									$ 0.4	$ 0.4