Indemnity Supplemental Information (Details) (USD $) In Millions, unless otherwise specified									3 Months Ended		6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009	Jun. 30, 2011 Indemnity	Dec. 31, 2010 Indemnity	Jun. 30, 2010 Indemnity	Dec. 31, 2009 Indemnity	Jun. 30, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Jun. 30, 2010 Indemnity Erie Family Life Insurance Company ("EFL")	Jun. 30, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Mar. 31, 2011 Indemnity Erie Family Life Insurance Company ("EFL")	Jun. 30, 2011 Exchange	Dec. 31, 2010 Exchange	Dec. 31, 2009 Exchange	Jun. 30, 2011 Reclassifications and eliminations	Dec. 31, 2010 Reclassifications and eliminations
Available-for-sale securities, at fair value:
Fixed maturities	$ 7,905	$ 7,543			$ 525	$ 264							$ 7,380	$ 7,279
Equity securities	630	594			20	24							610	570
Trading securities, at fair value	2,543	2,334			30	28							2,513	2,306
Limited partnerships	1,390	1,324			224	216							1,166	1,108
Other invested assets	20	20			1	1							19	19
Total investments	12,488	11,815			800	533							11,688	11,282
Cash and cash equivalents	109	430	223	234	48	310	34	76					61	120
Premiums receivable from policyholders	1,017	942											1,017	942
Reinsurance recoverable	198	201											198	201
Deferred acquisition costs	484	467											484	467
Other assets	427	489			111	132							316	357
Receivables from Exchange and other affiliates					265	232										(265)	(232)
Note receivable from EFL					25	25										(25)	(25)
Equity in EFL						80											(80)
Total assets	14,723	14,344			1,249	1,312							13,764	13,369		(290)	(337)
Liabilities
Losses and loss expense reserves	3,791	3,584											3,791	3,584
Life policy and deposit contract reserves	1,637	1,603											1,637	1,603
Unearned premiums	2,196	2,082											2,196	2,082
Deferred income taxes	251	283			1	26							250	257
Other liabilities, prior to consolidation eliminations					382	374							374	341
Other liabilities	466	458			390	382							76	76		(290)	(257)
Total liabilities	8,341	8,010			383	400							8,248	7,867		(290)	(257)
Indemnity's shareholders' equity
Total Indemnity shareholders' equity	866	912			866	912
Noncontrolling interest in consolidated entity - Exchange, prior to consolidation eliminations													5,516	5,502
Noncontrolling interest in consolidated entity - Exchange	5,516	5,422											5,516	5,422			(80)
Total equity, prior to consolidation eliminations					866	912							5,516	5,502
Total equity	6,382	6,334		5,725	866	912		902					5,516	5,422	4,823		(80)
Total liabilities, shareholders' equity and noncontrolling interest	14,723	14,344			1,249	1,312							13,764	13,369		(290)	(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