Reinsurance (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reinsurance
Direct life insurance in force	$ 4,562,000,000	$ 4,272,000,000	$ 4,043,000,000
Ceded life insurance in force	90,000,000	79,000,000	76,000,000
Property and Casualty Group
Reinsurance
Coverage under the first property catastrophe treaty as a percentage of the loss coverage amount	90.00%
Loss coverage amount, under first property catastrophe treaty, in excess of the Property & Casualty Groups retention per occurrence	500,000,000
Property & Casualty Group's retention per occurrence on first property catastrophe treaty	350,000,000
Coverage under the second property catastrophe treaty as a percentage of the loss coverage amount	70.00%
Loss coverage amount, under second property catastrophe treaty, in excess of $850,000,000	275,000,000
Loss threshold for second property catastrophe treaty to be triggered	850,000,000
Coverage under the third property catastrophe treaty as a percentage of the loss coverage amount	70.00%
Loss coverage amount, under third property catastrophe treaty, in excess of $1,125,000,000	25,000,000
Loss threshold for third property catastrophe treaty to be triggered	1,125,000,000
Coverage under the first renewed property catastrophe treaty as a percentage of the loss coverage amount	90.00%
Loss coverage amount, under first renewed property catastrophe treaty, in excess of the Property & Casualty Group's retention per occurrence	550,000,000
Property & Casualty Group's retention per occurrence on first renewed property catastrophe treaty	350,000,000
Coverage under the second renewed property catastrophe treaty as a percentage of the loss coverage amount	70.00%
Loss coverage amount, under second renewed property catastrophe treaty, in excess of $900,000,000	225,000,000
Loss threshold for second renewed property catastrophe treaty to be triggered	900,000,000
Coverage under the third renewed property catastrophe treaty as a percentage of the loss coverage amount	70.00%
Loss coverage amount, under third renewed property catastrophe treaty, in excess of $1,125,000,000	25,000,000
Loss threshold for third renewed property catastrophe treaty to be triggered	1,125,000,000
Property and Casualty Group | Minimum
Reinsurance
Reinsurance pooling agreement, termination notice period (in days)	365 days
Property and Casualty Group | Maximum
Reinsurance
Reinsurance pooling agreement, intercompany cash settlement period (in days)	30 days
Life insurance in force | Erie Family Life Insurance Company (EFL)
Reinsurance
Direct life insurance in force	44,000,000,000	42,000,000,000
Ceded life insurance in force	22,000,000,000	23,000,000,000
Largest amount of in force life insurance ceded to a single reinsurer	$ 11,000,000,000	$ 11,000,000,000
Erie Insurance Company | Property and Casualty Group
Reinsurance
Reinsurance pooling agreement, participation (as a percent)	5.00%
Erie Insurance Company of New York | Property and Casualty Group
Reinsurance
Reinsurance pooling agreement, participation (as a percent)	0.50%
Exchange | Property and Casualty Group
Reinsurance
Reinsurance pooling agreement, participation (as a percent)	94.50%