Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Revenues
Premiums earned/life policy revenue	$ 1,472	$ 1,355	$ 4,308	$ 3,962
Net investment income	120	115	360	335
Net realized investment (losses) gains	(292)	(85)	(243)	104
Net impairment losses recognized in earnings	(4)	(1)	(8)	(1)
Equity in earnings of limited partnerships	43	34	143	111
Service agreement and other revenue	7	8	23	24
Total revenues	1,346	1,426	4,583	4,535
Benefits and expenses
Insurance losses and loss expenses	939	935	2,975	3,095
Policy acquisition and underwriting expenses	367	341	1,076	987
Total benefits and expenses	1,306	1,276	4,051	4,082
Income (loss) from operations before income taxes and noncontrolling interest	40	150	532	453
Provision for income taxes	7	42	166	133
Net income (loss)	33	108	366	320	$ 573
Indemnity
Revenues
Net investment income	4	4	13	12
Net realized investment (losses) gains	0	0	0	1
Equity in earnings of limited partnerships	4	4	17	13
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	75	70	220	214
Provision for income taxes	25	23	75	72
Net income (loss)			145		168
Exchange
Revenues
Net investment income	116	111	347	323
Net realized investment (losses) gains	(292)	(85)	(243)	103
Equity in earnings of limited partnerships	39	30	126	98
Benefits and expenses
Net income (loss)			$ 221		$ 405
Management operations | Indemnity
Segment information
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)			25.00%
Revenues
Management fee revenue	389	362	$ 1,127	1,047
Service agreement and other revenue	7	8	22	23
Total revenues	396	370	1,149	1,070
Benefits and expenses
Cost of management operations	328	308	958	882
Income (loss) from operations before income taxes and noncontrolling interest	68	62	191	188
Investment operations | Indemnity
Revenues
Net investment income	4	4	13	12
Net realized investment (losses) gains	0	0	0	1
Net impairment losses recognized in earnings	(1)	0	(1)	0
Equity in earnings of limited partnerships	4	4	17	13
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	7	8	29	26
Operating segment | Management operations
Revenues
Management fee revenue	389	362	1,127	1,047
Service agreement and other revenue	7	8	22	23
Total revenues	396	370	1,149	1,070
Benefits and expenses
Cost of management operations	328	308	958	882
Total benefits and expenses	328	308	958	882
Income (loss) from operations before income taxes and noncontrolling interest	68	62	191	188
Provision for income taxes	24	22	67	66
Net income (loss)	44	40	$ 124	122
Operating segment | Management operations | Indemnity
Segment information
Indemnity's maximum management fee rate as a percent of premiums written and assumed by the Exchange (as a percent)			25.00%
Operating segment | Property and casualty insurance operations
Revenues
Premiums earned/life policy revenue	1,447	1,333	$ 4,239	3,899
Total revenues	1,447	1,333	4,239	3,899
Benefits and expenses
Insurance losses and loss expenses	912	908	2,897	3,016
Policy acquisition and underwriting expenses	420	387	1,222	1,132
Total benefits and expenses	1,332	1,295	4,119	4,148
Income (loss) from operations before income taxes and noncontrolling interest	115	38	120	(249)
Provision for income taxes	40	13	42	(87)
Net income (loss)	75	25	78	(162)
Operating segment | Life insurance operations
Revenues
Premiums earned/life policy revenue	25	22	69	64
Service agreement and other revenue	0	0	1	1
Total revenues	25	22	70	65
Benefits and expenses
Insurance losses and loss expenses	28	28	81	83
Policy acquisition and underwriting expenses	10	10	29	28
Total benefits and expenses	38	38	110	111
Income (loss) from operations before income taxes and noncontrolling interest	(13)	(16)	(40)	(46)
Provision for income taxes	(5)	(5)	(14)	(16)
Net income (loss)	(8)	(11)	(26)	(30)
Operating segment | Life insurance operations | Erie Family Life Insurance Company (EFL)
Segment information
Total investment revenues	24	26	74	79
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	11	10	34	33
Operating segment | Investment operations
Revenues
Net investment income	123	118	369	346
Net realized investment (losses) gains	(292)	(85)	(243)	104
Net impairment losses recognized in earnings	(4)	(1)	(8)	(1)
Equity in earnings of limited partnerships	43	34	143	111
Total revenues	(130)	66	261	560
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	(130)	66	261	560
Provision for income taxes	(52)	12	71	170
Net income (loss)	(78)	54	190	390
Eliminations
Revenues
Premiums earned/life policy revenue	0	0	0	(1)
Net investment income	(3)	(3)	(9)	(11)
Management fee revenue	(389)	(362)	(1,127)	(1,047)
Total revenues	(392)	(365)	(1,136)	(1,059)
Benefits and expenses
Cost of management operations	(328)	(308)	(958)	(882)
Insurance losses and loss expenses	(1)	(1)	(3)	(4)
Policy acquisition and underwriting expenses	(63)	(56)	(175)	(173)
Total benefits and expenses	$ (392)	$ (365)	$ (1,136)	$ (1,059)