Maximum percentage of employee compensation the employee may defer under a deferred compensation plan of the Company.

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Represents the Company's number of deferred compensation plans for directors.

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Period over which vested share credits will be paid upon separation from service.

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The maximum number of shares that may be earned by any single participant during any specified period, which may be a specified performance period or calendar year, net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan.

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The weighted average share price for shares delivered to participants under the plan.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of cash paid related to share-based compensation liabilities.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The weighted average of per share prices paid for shares purchased on the open market for issuance to employees under the plan.

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The number of shares purchased on the open market during the period for issuance to employees under the plan.

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Percentage of vesting of share-based compensation awards.

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Incentive and Deferred Compensation Plans - Narrative (Details)	1 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) Plans $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares
Incentive and deferred compensation plans
Number of incentive plans for executives, senior vice presidents and other selected officers \| Plans			2
Number of deferred compensation plans for executives, senior vice presidents and other selected officers \| Plans			2
Number of deferred compensation plans for outside directors \| Plans			2
Class A Common Stock
Incentive and deferred compensation plans
Total cost of shares purchased outside of publicly announced stock repurchase program			$ 3,200,000	$ 7,300,000	$ 1,500,000
Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares			27,120	60,332	15,093
Annual incentive plan
Incentive and deferred compensation plans
Maximum percentage of employee compensation that can be deferred			100.00%
Long-term incentive plan
Incentive and deferred compensation plans
Maximum percentage of employee compensation that can be deferred			100.00%
Vesting period of performance and/or service condition(s)			3 years
Maximum dollar amount which may be received by any single participant during any specified period			$ 5,000,000
Compensation cost related to share-based compensation plan awards			6,300,000	$ 10,300,000	$ 8,200,000
Tax benefits recognized in income related to award expense			1,300,000	$ 3,600,000	$ 2,900,000
Total unrecognized compensation cost related to share-based compensation plan awards pertaining to open performance periods			$ 5,700,000
Expected period of recognition related to unrecognized compensation cost			2 years
Long-term incentive plan \| Class A Common Stock
Incentive and deferred compensation plans
Maximum number of shares authorized for grant \| shares			1,500,000
Maximum number of shares which may be received by any single participant during any specified period \| shares			250,000
Average price per share for shares purchased \| $ / shares				$ 122.40	$ 98.20
Total cost of shares purchased outside of publicly announced stock repurchase program				$ 5,700,000	$ 800,000
Long-term incentive plan \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares				46,884	7,661
Long-term incentive plan \| Performance Period Long-Term Incentive Plan 2016-2018
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards			$ 7,400,000
Long-term incentive plan \| Performance Period Long-Term Incentive Plan 2015-2017
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards	$ 8,300,000
Long-term incentive plan \| Performance Period Long-Term Incentive Plan 2014-2016
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards		$ 4,700,000
Long-term incentive plan \| Performance Period Long-Term Incentive Plan 2014-2016 \| Class A Common Stock
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards		$ 5,900,000
Average price per share for shares delivered \| $ / shares		$ 126.21
Long-term incentive plan \| Performance Period Long-Term Incentive Plan 2014-2016 \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares		46,884
Incentive compensation deferral plan
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards			$ 700,000	$ 1,400,000
Vesting percent of the grant in Class A common stock			100.00%
Payment period for vested share credits			3 years
Incentive compensation deferral plan \| Class A Common Stock
Incentive and deferred compensation plans
Average price per share for shares purchased \| $ / shares			$ 119.28
Total cost of shares purchased outside of publicly announced stock repurchase program			$ 1,400,000
Incentive compensation deferral plan \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares			12,005
Stock compensation plan for outside directors
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards			$ 800,000	$ 900,000	$ 500,000
Stock compensation plan for outside directors \| Class A Common Stock
Incentive and deferred compensation plans
Average price per share for shares purchased \| $ / shares			$ 122.19	$ 121.85	$ 99.23
Total cost of shares purchased outside of publicly announced stock repurchase program			$ 1,100,000	$ 1,200,000	$ 700,000
Stock compensation plan for outside directors \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares			9,285	9,663	7,432
Stock compensation plan for outside directors \| Three Month Vesting Period \| Class A Common Stock
Incentive and deferred compensation plans
Vesting period of performance and/or service condition(s)			3 months
Vesting percent of the grant in Class A common stock			25.00%
Equity compensation plan
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards			$ 400,000	$ 200,000	$ 800,000
Total unrecognized compensation cost related to share-based compensation plan awards pertaining to open performance periods			$ 300,000
Expected period of recognition related to unrecognized compensation cost			3 years
Equity compensation plan \| Class A Common Stock
Incentive and deferred compensation plans
Maximum number of shares authorized for grant \| shares			100,000
Maximum number of shares which may be received by any single participant during any specified period \| shares			5,000
Average price per share for shares purchased \| $ / shares			$ 117.39	$ 111.55
Total cost of shares purchased outside of publicly announced stock repurchase program			$ 700,000	$ 400,000
Equity compensation plan \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares			5,830	3,785
Equity compensation plan \| Performance Period Equity Compensation Plan 2014-2015 \| Class A Common Stock
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards			$ 700,000
Average price per share for shares delivered \| $ / shares			$ 115.45
Equity compensation plan \| Performance Period Equity Compensation Plan 2014-2015 \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares			5,830
Equity compensation plan \| Performance Period Equity Compensation Plan 2014 \| Class A Common Stock
Incentive and deferred compensation plans
Compensation cost related to share-based compensation plan awards				$ 400,000
Average price per share for shares delivered \| $ / shares				$ 109.41
Equity compensation plan \| Performance Period Equity Compensation Plan 2014 \| Class A Common Stock \| Performance shares
Incentive and deferred compensation plans
Shares purchased outside of publicly announced stock repurchase program for share-based compensation awards \| shares				3,785
Erie Insurance Exchange (EIE) \| Long-term incentive plan
Incentive and deferred compensation plans
Incentive plan compensation cost reimbursed to Indemnity from the Exchange and its subsidiaries (as a percent)			47.00%
Erie Insurance Exchange (EIE) \| Incentive compensation deferral plan
Incentive and deferred compensation plans
Incentive plan compensation cost reimbursed to Indemnity from the Exchange and its subsidiaries (as a percent)			42.00%
Erie Insurance Exchange (EIE) \| Equity compensation plan
Incentive and deferred compensation plans
Incentive plan compensation cost reimbursed to Indemnity from the Exchange and its subsidiaries (as a percent)			68.00%	38.00%