Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Postretirement Benefits
Postretirement annual benefit expense reimbursed to Indemnity from the Exchange and EFL (as a percent)			57.00%
Cost of pension plans
Service cost for benefits earned	$ 8	$ 6	$ 23	$ 17
Interest cost on benefits obligation	8	7	23	21
Expected return on plan assets	(9)	(8)	(27)	(24)
Prior service cost amortization	0	0	1	1
Net actuarial loss amortization	3	2	10	5
Pension plan cost	10	$ 7	30	$ 20
Employee pension plan
Postretirement Benefits
Employer contributions			17
Erie Family Life Insurance Company (EFL) | Employee pension plan
Postretirement Benefits
Contingent liability for amount of nonparticipating annuity contracts the employee pension plan purchased from EFL	$ 23		$ 23