Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Revenues
Premiums earned/life policy revenue	$ 1,434	$ 1,319	$ 2,836	$ 2,607
Net investment income	127	111	240	220
Net realized investment (losses) gains	(7)	133	49	189
Net impairment losses recognized in earnings	(2)	0	(4)	0
Equity in earnings of limited partnerships	72	27	100	77
Service agreement and other revenue	8	8	16	16
Total revenues	1,632	1,598	3,237	3,109
Benefits and expenses
Insurance losses and loss expenses	976	1,126	2,036	2,160
Policy acquisition and underwriting expenses	361	325	709	646
Total benefits and expenses	1,337	1,451	2,745	2,806
Income (loss) from operations before income taxes and noncontrolling interest	295	147	492	303
Provision for income taxes	98	44	159	91
Net income (loss)	197	103	333	212	$ 573
Indemnity
Revenues
Net investment income	5	4	9	8
Net realized investment (losses) gains	0	0	0	1
Equity in earnings of limited partnerships	11	3	13	9
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	86	75	145	144
Provision for income taxes	30	26	50	49
Net income (loss)			95		168
Exchange
Revenues
Net investment income	122	107	231	212
Net realized investment (losses) gains	(7)	133	49	188
Equity in earnings of limited partnerships	61	24	87	68
Benefits and expenses
Net income (loss)			$ 238		$ 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	395	366	$ 738	685
Service agreement and other revenue	7	8	15	15
Total revenues	402	374	753	700
Benefits and expenses
Cost of management operations	332	306	630	574
Income (loss) from operations before income taxes and noncontrolling interest	70	68	123	126
Investment operations | Indemnity
Revenues
Net investment income	5	4	9	8
Net realized investment (losses) gains	0	0	0	1
Net impairment losses recognized in earnings	0	0	0	0
Equity in earnings of limited partnerships	11	3	13	9
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	16	7	22	18
Operating segment | Management operations
Revenues
Management fee revenue	395	366	738	685
Service agreement and other revenue	7	8	15	15
Total revenues	402	374	753	700
Benefits and expenses
Cost of management operations	332	306	630	574
Total benefits and expenses	332	306	630	574
Income (loss) from operations before income taxes and noncontrolling interest	70	68	123	126
Provision for income taxes	24	24	43	44
Net income (loss)	46	44	$ 80	82
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	1,412	1,298	$ 2,792	2,566
Total revenues	1,412	1,298	2,792	2,566
Benefits and expenses
Insurance losses and loss expenses	952	1,101	1,985	2,108
Policy acquisition and underwriting expenses	416	380	802	745
Total benefits and expenses	1,368	1,481	2,787	2,853
Income (loss) from operations before income taxes and noncontrolling interest	44	(183)	5	(287)
Provision for income taxes	16	(64)	2	(100)
Net income (loss)	28	(119)	3	(187)
Operating segment | Life insurance operations
Revenues
Premiums earned/life policy revenue	22	22	44	42
Service agreement and other revenue	1	0	1	1
Total revenues	23	22	45	43
Benefits and expenses
Insurance losses and loss expenses	25	27	53	55
Policy acquisition and underwriting expenses	10	9	19	18
Total benefits and expenses	35	36	72	73
Income (loss) from operations before income taxes and noncontrolling interest	(12)	(14)	(27)	(30)
Provision for income taxes	(4)	(5)	(9)	(11)
Net income (loss)	(8)	(9)	(18)	(19)
Operating segment | Life insurance operations | Erie Family Life Insurance Company (EFL)
Segment information
Total investment revenues	25	24	50	53
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	13	10	23	23
Operating segment | Investment operations
Revenues
Net investment income	130	116	246	228
Net realized investment (losses) gains	(7)	133	49	189
Net impairment losses recognized in earnings	(2)	0	(4)	0
Equity in earnings of limited partnerships	72	27	100	77
Total revenues	193	276	391	494
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	193	276	391	494
Provision for income taxes	62	89	123	158
Net income (loss)	131	187	268	336
Eliminations
Revenues
Premiums earned/life policy revenue	0	(1)	0	(1)
Net investment income	(3)	(5)	(6)	(8)
Management fee revenue	(395)	(366)	(738)	(685)
Total revenues	(398)	(372)	(744)	(694)
Benefits and expenses
Cost of management operations	(332)	(306)	(630)	(574)
Insurance losses and loss expenses	(1)	(2)	(2)	(3)
Policy acquisition and underwriting expenses	(65)	(64)	(112)	(117)
Total benefits and expenses	$ (398)	$ (372)	$ (744)	$ (694)