Reinsurance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015
Reinsurance
Insurance losses and loss expenses	$ 3,958	$ 3,467	$ 3,480
Property and Casualty Group
Reinsurance
Insurance losses and loss expenses	3,853	3,360	3,379
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
Property and Casualty Group | First property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence	100
Property & Casualty Group's retention amount per occurrence	300
Insurance losses and loss expenses	0
Property and Casualty Group | First property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)	30.00%
Property and Casualty Group | Second property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence	500
Property & Casualty Group's retention amount per occurrence	400
Insurance losses and loss expenses	0
Property and Casualty Group | Second property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)	90.00%
Property and Casualty Group | Third property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence	200
Property & Casualty Group's retention amount per occurrence	900
Insurance losses and loss expenses	0
Property and Casualty Group | Third property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)	85.00%
Property and Casualty Group | Fourth property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence	25
Property & Casualty Group's retention amount per occurrence	1,100
Insurance losses and loss expenses	0
Property and Casualty Group | Fourth property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)	100.00%
Property and Casualty Group | Effective for the next fiscal year | First property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence				100
Property & Casualty Group's retention amount per occurrence				300
Property and Casualty Group | Effective for the next fiscal year | First property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)				35.00%
Property and Casualty Group | Effective for the next fiscal year | Second property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence				500
Property & Casualty Group's retention amount per occurrence				400
Property and Casualty Group | Effective for the next fiscal year | Second property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)				90.00%
Property and Casualty Group | Effective for the next fiscal year | Third property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence				200
Property & Casualty Group's retention amount per occurrence				900
Property and Casualty Group | Effective for the next fiscal year | Third property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)				86.00%
Property and Casualty Group | Effective for the next fiscal year | Fourth property catastrophe reinsurance treaty
Reinsurance
Loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence				25
Property & Casualty Group's retention amount per occurrence				$ 1,100
Property and Casualty Group | Effective for the next fiscal year | Fourth property catastrophe reinsurance treaty | Maximum
Reinsurance
Percentage of loss coverage amount in excess of the Property & Casualty Group's loss retention per occurrence (as a percent)				100.00%
Property and Casualty Group | Exchange
Reinsurance
Reinsurance pooling agreement, participation (as a percent)	94.50%
Property and Casualty Group | Erie Insurance Company (EIC)
Reinsurance
Reinsurance pooling agreement, participation (as a percent)	5.00%
Property and Casualty Group | Erie Insurance Company of New York (ENY)
Reinsurance
Reinsurance pooling agreement, participation (as a percent)	0.50%