Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Revenues
Premiums earned/life policy revenue	$ 1,402	$ 1,288
Net investment income	113	109
Net realized investment gains	56	56
Net impairment losses recognized in earnings	(2)	0
Equity in earnings of limited partnerships	28	50
Service agreement and other revenue	8	8
Total revenues	1,605	1,511
Benefits and expenses
Insurance losses and loss expenses	1,060	1,034
Policy acquisition and underwriting expenses	348	321
Total benefits and expenses	1,408	1,355
Income (loss) from operations before income taxes and noncontrolling interest	197	156
Provision for income taxes	61	47
Net income (loss)	136	109	573
Indemnity
Revenues
Net investment income	4	4
Net realized investment gains	0	1
Equity in earnings of limited partnerships	2	6
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	59	69
Provision for income taxes	20	23
Net income (loss)	39		168
Exchange
Revenues
Net investment income	109	105
Net realized investment gains	56	55
Equity in earnings of limited partnerships	26	44
Benefits and expenses
Net income (loss)	97		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	343	319
Service agreement and other revenue	8	7
Total revenues	351	326
Benefits and expenses
Cost of management operations	298	268
Income (loss) from operations before income taxes and noncontrolling interest	53	58
Investment operations | Indemnity
Revenues
Net investment income	4	4
Net realized investment gains	0	1
Net impairment losses recognized in earnings	0	0
Equity in earnings of limited partnerships	2	6
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	6	11
Operating segment | Management operations
Revenues
Management fee revenue	343	319
Service agreement and other revenue	8	7
Total revenues	351	326
Benefits and expenses
Cost of management operations	298	268
Total benefits and expenses	298	268
Income (loss) from operations before income taxes and noncontrolling interest	53	58
Provision for income taxes	19	20
Net income (loss)	34	38
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	1,380	1,268
Total revenues	1,380	1,268
Benefits and expenses
Insurance losses and loss expenses	1,033	1,007
Policy acquisition and underwriting expenses	386	365
Total benefits and expenses	1,419	1,372
Income (loss) from operations before income taxes and noncontrolling interest	(39)	(104)
Provision for income taxes	(14)	(36)
Net income (loss)	(25)	(68)
Operating segment | Life insurance operations
Revenues
Premiums earned/life policy revenue	22	20
Service agreement and other revenue	0	1
Total revenues	22	21
Benefits and expenses
Insurance losses and loss expenses	28	28
Policy acquisition and underwriting expenses	9	9
Total benefits and expenses	37	37
Income (loss) from operations before income taxes and noncontrolling interest	(15)	(16)
Provision for income taxes	(5)	(6)
Net income (loss)	(10)	(10)
Operating segment | Life insurance operations | Erie Family Life Insurance Company (EFL)
Segment information
Total investment revenues	25	29
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	10	13
Operating segment | Investment operations
Revenues
Net investment income	116	112
Net realized investment gains	56	56
Net impairment losses recognized in earnings	(2)	0
Equity in earnings of limited partnerships	28	50
Total revenues	198	218
Benefits and expenses
Income (loss) from operations before income taxes and noncontrolling interest	198	218
Provision for income taxes	61	69
Net income (loss)	137	149
Eliminations
Revenues
Premiums earned/life policy revenue	0	0
Net investment income	(3)	(3)
Management fee revenue	(343)	(319)
Total revenues	(346)	(322)
Benefits and expenses
Cost of management operations	(298)	(268)
Insurance losses and loss expenses	(1)	(1)
Policy acquisition and underwriting expenses	(47)	(53)
Total benefits and expenses	$ (346)	$ (322)