Indemnity Supplemental Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed financial statements
Service agreement revenue	$ 8	$ 9
Total revenues	1,520	1,365
Total benefits and expenses	986	953
Net investment income	108	105
Net realized gains on investments	296	149
Net impairment losses recognized in earnings	0	0
Equity in earnings of limited partnerships	21	72
Income from operations before income taxes and noncontrolling interest	534	412
Provision for income taxes	180	138
Net income	36	44
Indemnity
Condensed financial statements
Net investment income	4	4
Net realized gains on investments	3	1
Income from operations before income taxes and noncontrolling interest	54	67
Provision for income taxes	18	23
Net income	36	44
Indemnity | Management operations
Condensed financial statements
Management fee revenue, net	269	251
Service agreement revenue	7	8
Total revenues	276	259
Cost of management operations	230	211
Income from operations before income taxes and noncontrolling interest	46	48
Percent income attributable to Indemnity shareholder interest	100.00%	100.00%
Indemnity | Life insurance operations
Condensed financial statements
Total revenues		10
Total benefits and expenses		7
Income from operations before income taxes and noncontrolling interest		3
Percent income attributable to Indemnity shareholder interest		21.60%
Indemnity | Investment operations
Condensed financial statements
Net investment income	4	4
Net realized gains on investments	3	1
Net impairment losses recognized in earnings	0	0
Equity in earnings of limited partnerships	1	11
Income from operations before income taxes and noncontrolling interest	8	16
Indemnity | Erie Family Life Insurance Company ("EFL")
Condensed financial statements
Indemnity's ownership interest in EFL prior to and through March 31, 2011 (as a percent)		21.60%
Indemnity's ownership interest in EFL sold to the Exchange (as a percent)		21.60%
Exchange
Condensed financial statements
Net investment income	104	101
Net realized gains on investments	293	148
Net impairment losses recognized in earnings	$ (0.1)
Exchange | Erie Family Life Insurance Company ("EFL")
Condensed financial statements
Exchange's ownership interest in EFL prior to and through March 31, 2011 (as a percent)		78.40%
Exchange's ownership interest in EFL after March 31, 2011 (as a percent)		100.00%