Indemnity Supplemental Information (Details) (USD $) In Millions, unless otherwise specified									3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Indemnity	Dec. 31, 2012 Indemnity	Mar. 31, 2012 Indemnity	Dec. 31, 2011 Indemnity	Mar. 31, 2013 Indemnity Erie Family Life Insurance Company ("EFL")	Mar. 31, 2012 Indemnity Erie Family Life Insurance Company ("EFL")	Dec. 31, 2012 Indemnity Erie Family Life Insurance Company ("EFL")	Mar. 31, 2013 Exchange	Dec. 31, 2012 Exchange	Dec. 31, 2011 Exchange	Mar. 31, 2013 Reclassifications and eliminations	Dec. 31, 2012 Reclassifications and eliminations
Available-for-sale securities, at fair value:
Fixed maturities	$ 8,312	$ 8,159			$ 421	$ 452						$ 7,891	$ 7,707
Equity securities	992	1,000			49	55						943	945
Trading securities, at fair value	2,662	2,417			0	0						2,662	2,417
Limited partnerships	1,171	1,217			167	180						1,004	1,037
Other invested assets	21	21			1	1						20	20
Total investments	13,158	12,814			638	688						12,520	12,126
Cash and cash equivalents	388	400	199	185	41	12	28	11				347	388
Premiums receivable from policyholders	1,113	1,062										1,113	1,062
Reinsurance recoverable	169	168										169	168
Deferred income taxes	39	37			39	37						0	0
Deferred acquisition costs	510	504										510	504
Other assets	414	456			115	117						299	339
Receivables from the Exchange and other affiliates					287	281			4		3				(287)	(281)
Note receivable from EFL					25	25									(25)	(25)
Total assets	15,791	15,441			1,145	1,160						14,958	14,587		(312)	(306)
Liabilities
Losses and loss expense reserves	3,628	3,598										3,628	3,598
Life policy and deposit contract reserves	1,726	1,708										1,726	1,708
Unearned premiums	2,399	2,365										2,399	2,365
Deferred income taxes	410	365			0	0						410	365
Other liabilities, adjusted for consolidation presentation	611	614			509	518						414	402		(312)	(306)
Total liabilities	8,774	8,650			509	518						8,577	8,438		(312)	(306)
Shareholders' equity and noncontrolling interest
Total Indemnity shareholders' equity	636	642			636	642
Noncontrolling interest in consolidated entity - Exchange	6,381	6,149										6,381	6,149
Total equity	7,017	6,791		6,293	636	642		781				6,381	6,149	5,512
Total liabilities, shareholders' equity and noncontrolling interest	15,791	15,441			1,145	1,160						14,958	14,587		(312)	(306)
Recievables from the Exchange					283	278
Note receivable from EFL, annual interest rate (as a percent)									6.70%
Note receivable from EFL, interest income recognized by Indemnity									$ 0.4	$ 0.4