Indemnity Supplemental Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale securities, at fair value:
Fixed maturities	$ 10,055		$ 9,571
Equity securities	862		875
Trading securities, at fair value	3,096		3,223
Limited partnerships	915		979
Other invested assets	22		21
Total investments	14,950		14,669
Cash and cash equivalents	420	379	514	452
Premiums receivable from policyholders	1,304		1,281
Reinsurance recoverable	162		161
Deferred income tax asset	40		37
Deferred acquisition costs	589		595
Other assets	528		501
Total assets	17,993		17,758
Liabilities
Losses and loss expense reserves	3,966		3,853
Life policy and deposit contract reserves	1,827		1,812
Unearned premiums	2,845		2,834
Deferred income tax liability	494		490
Other liabilities, adjusted for consolidation presentation	724		786
Total liabilities	9,856		9,775
Shareholders' equity and noncontrolling interest
Total Indemnity shareholders' equity	710		703
Noncontrolling interest in consolidated entity - Exchange	7,427		7,280
Total equity	8,137		7,983	7,550
Total liabilities, shareholders' equity, and noncontrolling interest	17,993		17,758
Indemnity
Available-for-sale securities, at fair value:
Fixed maturities	556		564
Equity securities	25		25
Limited partnerships	100		113
Other invested assets	1		1
Total investments	682		703
Cash and cash equivalents	58	44	92	49
Deferred income tax asset	40		37
Other assets	125		127
Receivables from the Exchange and other affiliates	337		335
Note receivable from EFL	25		25
Total assets	1,267		1,319
Liabilities
Deferred income tax liability	0		0
Other liabilities, adjusted for consolidation presentation	557		616
Total liabilities	557		616
Shareholders' equity and noncontrolling interest
Total Indemnity shareholders' equity	710		703
Total equity	710		703	734
Total liabilities, shareholders' equity, and noncontrolling interest	1,267		1,319
Exchange
Available-for-sale securities, at fair value:
Fixed maturities	9,499		9,007
Equity securities	837		850
Trading securities, at fair value	3,096		3,223
Limited partnerships	815		866
Other invested assets	21		20
Total investments	14,268		13,966
Cash and cash equivalents	362		422
Premiums receivable from policyholders	1,304		1,281
Reinsurance recoverable	162		161
Deferred income tax asset	0		0
Deferred acquisition costs	589		595
Other assets	403		374
Total assets	17,088		16,799
Liabilities
Losses and loss expense reserves	3,966		3,853
Life policy and deposit contract reserves	1,827		1,812
Unearned premiums	2,845		2,834
Deferred income tax liability	494		490
Other liabilities, adjusted for consolidation presentation	529		530
Total liabilities	9,661		9,519
Shareholders' equity and noncontrolling interest
Noncontrolling interest in consolidated entity - Exchange	7,427		7,280
Total equity	7,427		7,280	6,816
Total liabilities, shareholders' equity, and noncontrolling interest	17,088		16,799
Receivables from the Exchange and other affiliates	332		331
Erie Family Life Insurance Company (EFL)
Available-for-sale securities, at fair value:
Note receivable from EFL	25
Shareholders' equity and noncontrolling interest
Receivables from the Exchange and other affiliates	5		4
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
Reclassifications and eliminations
Available-for-sale securities, at fair value:
Receivables from the Exchange and other affiliates	(337)		(335)
Note receivable from EFL	(25)		(25)
Total assets	(362)		(360)
Liabilities
Other liabilities, adjusted for consolidation presentation	(362)		(360)
Total liabilities	(362)		(360)
Shareholders' equity and noncontrolling interest
Total liabilities, shareholders' equity, and noncontrolling interest	$ (362)		$ (360)