Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended								12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Indemnity	Dec. 31, 2011 Indemnity	Dec. 31, 2010 Indemnity	Dec. 31, 2010 Indemnity Erie Family Life Insurance Company (EFL)	Mar. 31, 2011 Indemnity Erie Family Life Insurance Company (EFL)	Dec. 31, 2012 Exchange	Dec. 31, 2011 Exchange	Dec. 31, 2010 Exchange
Income taxes
Current income tax expense (benefit)				$ 84	$ 85	$ 37			$ 78	$ 110	$ (43)
Deferred income tax expense (benefit)	118	(105)	342	(3)	0	67			121	(105)	278
Total provision for income taxes	280	90	339	81	85	104			199	5	235
Increase in Indemnity's deferred tax liability recorded for its investment in EFL as a result of a change in the tax rate used to calculate the liability							18
Indemnity's ownership interest in EFL sold to the Exchange (as a percent)								21.60%
Deduction available for dividends received (as a percent)							80.00%
reconciliation of the provision for income taxes, with amounts determined by applying the statutory federal income tax rates to pre-tax income
Income tax at statutory rates				84	89	93			230	37	259
Tax-exempt interest				(2)	(3)	(3)			(13)	(15)	(16)
Dividends received deduction				(1)	(1)	(1)			(14)	(13)	(11)
Deferred tax valuation allowance				0	0	(2)			0	0	(4)
Erie Family Life earnings (losses)				0	(1)	15
Goodwill impairments									0	0	8
Return to provision adjustments									(3)	(5)	0
Other, net				0	1	2			(1)	1	(1)
Provision for income taxes	$ 280	$ 90	$ 339	$ 81	$ 85	$ 104			$ 199	$ 5	$ 235
Indemnity's effective income tax rate on its share of EFL earnings, prior to decision to sell its ownership interest (as a percent)							7.00%
Indemnity's effective income tax rate on its share of EFL earnings, after decision to sell its ownership interest (as a percent)							35.00%