Due after five years through ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Agent bonus estimates Selling, General and Administrative Expense [Abstract] Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Agent loans, net Financing Receivable, after Allowance for Credit Loss, Noncurrent Investment securities: AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Actuarial (gain) loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Leasehold improvements Leasehold Improvements [Member] Reconciliation of the provision for income taxes, with amounts determined by applying the statutory federal income tax rate to pre-tax income Effective Income Tax Rate Reconciliation, Amount [Abstract] Risks and Uncertainties [Abstract] Risks and Uncertainties [Abstract] Available-for-sale securities Debt Securities, Available-for-sale, Current Compensation deferred Deferred Compensation Arrangement with Individual Liability Incurred During Period The liability incurred during the period to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit. Level 3 changes Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Dividends declared Dividends, Common Stock, Cash Security Exchange Name Security Exchange Name Equity securities Equity Securities, FV-NI, Current Pension and other postretirement plans Pension and other postretirement plans, OCI (loss) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent OCI (loss) Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent Cost of pension plans: Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Minimum multiplier for dividend payable on Class A common stock per dividend declared on Class B common stock Dividends Common Stock Percentage Multiplier Minimum Represents the minimum multiplier applied to a percentage of the dividend declared on Class B common stock to determine the required dividend on Class A common stock. Target asset allocation for the portfolio: Defined Benefit Plan, Plan Assets, Allocations [Abstract] Principal payments due in 2023 Long-Term Debt, Maturity, Year Two Schedule of Gain (Loss) on Securities [Table] Schedule of Gain (Loss) on Securities [Table] Management fee rate as a percent of direct and affiliated assumed written premiums of the exchange Insurance Agency Management Fee, Percent Represents the management fee rate, determined by the board of directors of the entity, calculated as a percentage of the direct and affiliated assumed written premiums. Performance period for agent bonuses Agent Bonus Performance Period Represents the period over which performance is measured for the estimation of agent bonuses. Pension liabilities – due within one year Liability, Defined Benefit Pension Plan, Current Secondary agent bonus Secondary Agent Bonus [Member] Information related to the secondary agent bonus plan. Schedule of Defined Contribution Plans Disclosures [Table] Schedule of Defined Contribution Plans Disclosures [Table] Schedule of Defined Contribution Plans Disclosures [Table] Approximate amount of repurchase authority remaining under the current stock repurchase program Stock Repurchase Program, Remaining Authorized Repurchase Amount Additions for prior year tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Net deferred tax asset Deferred Tax Assets, Net Indemnity revenue recognized Contract with Customer, Liability, Revenue Recognized Net purchase of treasury stock Net Treasury Stock Value Acquired Held And Reissued Equity impact of the cost of common stock that was repurchased under a publicly announced share repurchase program and equity impact of common stock repurchased, held, or reissued during the period for any equity-based compensation plan, recorded using the cost method. Subsequent Events [Abstract] Subsequent Events [Abstract] Investment Secondary Categorization [Axis] Investment Secondary Categorization [Axis] Industry Sector [Axis] Industry Sector [Axis] Interest payments due in 2023 Long-Term Debt, Repayments Of Interest In Year Two Long-Term Debt, Repayments Of Interest In Year Two International risk controlled equity International Risk Controlled Equity [Member] This category seeks long-term capital growth with an emphasis on controlling return volatility relative to an international market index. Schedule of Funded Status of Pension Plans and Amounts Recognized in the Statements of Financial Position Schedule of Net Funded Status And Amounts Recognized In Balance Sheet [Table Text Block] Tabular disclosure of net funded status of pension plans and/or other employee benefit plans and tabular disclosure of the amounts that are recognized in the balance sheet (or statement of financial position) for pension plans and/or other employee benefit plans, showing separately the assets and current and noncurrent liabilities (if applicable) recognized. Included in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Award Type [Domain] Award Type [Domain] Local Phone Number Local Phone Number Schedule of Reconciliation of Cost to Fair Value of Available-For-Sale Securities Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Net actuarial loss amortization Defined Benefit Plan, Amortization of Gain (Loss) Schedule of Amortized Cost and Estimated Fair Value of Available-For-Sale Securities by Remaining Contractual Term to Maturity Investments Classified by Contractual Maturity Date [Table Text Block] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Amendments Other Comprehensive Income Defined Benefit Plans Amendments During Period before Tax Amount, before tax, of other comprehensive income from plan amendments, that has not been recognized in net periodic benefit cost. Total cost of shares purchased for share-based compensation awards Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Share-based Liabilities Paid Retained earnings Retained Earnings [Member] Actuarial assumptions used to determine net periodic benefit cost: Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] Fixed assets, net Fixed assets, net Finite Lived Intangible Assets And Property Plant And Equipment Net Amount after amortization, accumulated depreciation and depletion, of assets, excluding financial assets and goodwill, lacking physical substance with a finite life and physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, capitalized internally developed software, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. Net investment income Net investment income Net Investment Income and Income (Loss) from Equity Method Investments Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest and amount of income (loss) for proportionate share of equity method investee's income (loss). Available-for-sale securities Available-for-sale securities Debt securities Debt Securities [Member] Investment income Investment Income, Nonoperating [Abstract] AOCI (loss), beginning of year AOCI (loss), end of year AOCI Tax, Attributable to Parent Unfunded plan Defined Benefit Plan, Unfunded Plan [Member] Net impairment recoveries (losses) recognized in earnings Available-For-Sale Debt Securities And Financing Receivables, Impairment (Loss) Recoveries Available-For-Sale Debt Securities And Financing Receivables, Impairment (Loss) Recoveries Recognized in Earnings Amounts recognized in other comprehensive income for pension plans: Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract] Reimbursements from the Exchange for lease costs and related operating expenses Rent Reimbursed from Related Party Represents rent and related operating expenses reimbursed from Erie Insurance Exchange and its subsidiaries. Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Performance Period Equity Compensation Plan 2016 Performance Period Equity Compensation Plan 2016 [Member] Represents the 2014 performance period under the entity's Equity Compensation Plan. Loans to agents Payments to Acquire Loans Receivable Performance obligations under subscriber's agreement Revenue, Performance Obligation, Number of Performance Obligations Number of performance obligations recognized by Indemnity acting as attorney-in-fact for the subscribers of the Exchange in accordance with Topic 606. Class A common stock - basic (in dollars per share) Per- share amount (in dollars per share) Earnings Per Share, Basic Less: net (losses) gains recognized on securities sold Equity Securities, FV-NI, Realized Gain (Loss) Revenue Revenue from Contract with Customer [Text Block] Tax-exempt interest Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Principal payments due in 2022 Long-Term Debt, Maturity, Year One Due after one year through five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Fair Value Measurement [Domain] Fair Value Measurement [Domain] Accounting Policies [Table] Accounting Policies [Table] Specific details of accounting policies, including the line items affected and the financial effects of those policies. Defined benefit pension plans Pension liabilities – due after one year Liability, Defined Benefit Pension Plan, Noncurrent Cumulative Effect, Period of Adoption, Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member] Depreciation Deferred Tax Liabilities, Property, Plant and Equipment Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Interest payments due in 2024 Long-Term Debt, Repayments Of Interest In Year Three Long-Term Debt, Repayments Of Interest In Year Three Entity Voluntary Filers Entity Voluntary Filers Total Defined Benefit Plan, Plan Assets, Category [Domain] Plan Name [Axis] Plan Name [Axis] Long-term borrowings Long-term Debt Level 1 Level 1 Fair Value, Inputs, Level 1 [Member] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Entity Small Business Entity Small Business Class B common stock shares converted into Class A common stock shares (in shares) Conversion of Stock, Shares Converted Schedule of Impairments on Available-For-Sale Securities and Agent Loans Financing Receivable, Allowance for Credit Loss [Table Text Block] Deferred executive compensation Deferred Compensation Liability, Current Scenario [Axis] Scenario [Axis] Plan amendments Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Deferred compensation Deferred Compensation [Member] Deferred compensation arrangement (such as stock or unit options and share or unit awards) that is equity-based payments with participants. The arrangement is based on an agreement between the entity and the participant, and contains a promise by the entity to pay certain amounts or benefits at designated future dates, upon compliance with stipulated requirements. Service agreement revenue Service Agreement [Member] Service charges we collect from subscribers/policyholders for providing extended payment terms on policies written and assumed by the Exchange, and late payment and policy reinstatement fees.  The service charges are fixed dollar amounts per billed installment. Also included is service agreement revenue from shared office space based on utilization statistics. Liabilities and shareholders' equity Liabilities and Equity [Abstract] Investment Income [Table] Investment Income [Table] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities, Current Performance Period Equity Compensation Plan 2017 Performance Period Equity Compensation Plan 2017 [Member] Represents the 2014-2015 performance period under the entity's Equity Compensation Plan. Equity securities Equity Securities, FV-NI, Gain (Loss) Entity Interactive Data Current Entity Interactive Data Current Principal payments due thereafter Long-Term Debt, Maturity, after Year Five Gross realized gains Debt Securities, Available-for-sale, Realized Gain Class of Stock Disclosures [Abstract] Class of Stock Disclosures [Abstract] Available-for-sale securities: Debt Securities, Available-for-sale, Allowance for Credit Loss [Abstract] Balance at the beginning of the year Balance at the end of the year Unrecognized Tax Benefits Total deferred tax assets Deferred Tax Assets, Gross Reconciliation of the numerators and denominators used in the basic and diluted per-share computations Schedule Of Earnings Per Share Basic And Diluted [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Equity securities: Equity Securities, FV-NI, Gain (Loss) [Abstract] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Gross unrealized gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Entity Address, State or Province Entity Address, State or Province Total contributed capital and retained earnings Stockholders' Equity before Treasury Stock Deferred income taxes, net Deferred Income Tax Assets, Net Rabbi trust distribution Distributions From Rabbi Trust Plans Distributions From Rabbi Trust Plans Current liabilities: Liabilities, Current [Abstract] International small capitalization risk controlled equity International Small Capitalization Risk Controlled Equity [Member] This category seeks to provide excess returns relative to an international small cap index, while maintaining regional weights similar to the index. Supplemental employee retirement plan (SERP) Supplemental Employee Retirement Plan [Member] Equity securities Total equity securities Equity Securities [Member] Accounting Policies [Abstract] Accounting Policies [Abstract] 2025 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Document Transition Report Document Transition Report Common stock Common Stock, Value, Issued Expected period of recognition related to unrecognized compensation cost Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Pre-retirement discount rate Defined Benefit Plan, Assumptions Used Calculating, Net Periodic Benefit Cost, Pre Retirement Discount Rate The pre-retirement interest rate used to adjust for the time value of money. Schedule of Financial Instruments Not Carried at Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Commercial mortgage-backed securities Commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Funded status at end of year Defined Benefit Plan, Funded (Unfunded) Status of Plan ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Other Commitments [Table] Other Commitments [Table] Agent compensation expense Agent Compensation Expense [Member] Scheduled commissions to agents based upon premiums written as well as additional commissions and bonuses to agents, which are earned by achieving targeted measures. Legal Entity [Axis] Legal Entity [Axis] Weighted shares (denominator) (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Amortization of prior service costs Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax Investments Marketable Securities, Policy [Policy Text Block] Class of Stock [Axis] Class of Stock [Axis] Land, buildings, and building improvements Land, Buildings and Improvements [Member] Interest capitalized costs incurred Interest Costs Incurred Employee benefits paid Pension Contributions and Payments for Other Labor Related Expenses Payments of cash for pension contributions, payroll tax expense, postemployment and benefit-related expenses not elsewhere specified in the taxonomy (such as health plan, profit sharing, incentives, tuition reimbursement, other fringe benefits and perquisites) during the current period. AOCI (loss), beginning of year AOCI (loss), end of year AOCI before Tax, Attributable to Parent Purchase of fixed assets Payments to Acquire Productive Assets Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Schedule of Roll Forward of Level 3 Fair Value Measurements on a Recurring Basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Entity [Domain] Entity [Domain] Dividends declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Total operating revenue Revenue from Contract with Customer, Excluding Assessed Tax Projected benefit obligations increase Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease) Income available to stockholders (Basic EPS:) Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Amortization of net actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Expense Classification [Axis] Expense Classification [Axis] Information by nature and type of expense. Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Agent loans Financing Receivable [Policy Text Block] Available-for-sale securities Debt Securities, Available-for-sale [Line Items] Due after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Increase (Decrease) in Shareholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Document Fiscal Year Focus Document Fiscal Year Focus Amount of loan participation program Amount of Loan Participation Program Amount of Loan Participation Program Operating expenses on office space leased from exchange Operating Costs and Expenses Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Other investments Payments to Acquire Other Investments Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Additional paid-in-capital Additional Paid-in Capital [Member] Maximum funding percentage of each loan Financing Receivable, before Allowance for Credit Loss, Participation Percentage Financing Receivable, before Allowance for Credit Loss, Participation Percentage 2027 - 2031 Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Annual incentive plan awards Other Labor-related Expenses U.S. corporate bonds with an emphasis on long duration bonds rated A or better Debt Security, Corporate, US [Member] Entity Information [Line Items] Entity Information [Line Items] Total payments due thereafter Long-Term Debt, Repayments Of Principal and Interest After Year Five Long-Term Debt, Repayments Of Principal and Interest After Year Five Agent loans Financing Receivable, after Allowance for Credit Loss Other (expense) income Other Nonoperating Income (Expense) Net realized and unrealized investment gains Net realized and unrealized investment gains Debt and Equity Securities, Gain (Loss) Industry Sector [Domain] Industry Sector [Domain] Deferred revenue Deferred Tax Assets, Deferred Income Maximum Maximum [Member] Schedule of provision for income taxes Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Schedule of Deferred Executive Compensation Liability Schedule Of Compensation Cost For Cash Based Incentive And Share Based Payments And Deferred Compensation, Allocation Of Costs By Plan [Table Text Block] Tabular disclosure of the amount of total cash-based incentive plan compensation cost, share/equity-based compensation cost, and deferred compensation arrangements, including the amounts related to awards, payments, deferrals, liabilities, and any tax benefits attributable to each plan. Award Type [Axis] Award Type [Axis] Total shareholders' equity Balance, beginning of year Balance, end of year Cumulative effect adjustment Stockholders' Equity Attributable to Parent City Area Code City Area Code Decrease in accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Schedule of Reconciliation of Net Income to Net Cash Provided by Operating Activities as Presented in the Statements of Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Expense Classification [Table] Expense Classification [Table] Describes the nature and type of expenses and the percentage that those expenses are to total expenses. Estimated useful life Property, Plant and Equipment, Useful Life Distributions from the deferred compensation plans Deferred Compensation Arrangement with Individual, Distribution Paid Shareholders' equity Stockholders' Equity Attributable to Parent [Abstract] Stock repurchases Equity, Class of Treasury Stock [Line Items] Adjustments for New Accounting Pronouncements [Axis] Accounting Standards Update [Axis] Current income tax expense Current Income Tax Expense (Benefit) Amount of senior secured draw term loan credit facility Debt Instrument, Face Amount Pension plan cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Tax benefits recognized in income related to award expense Share-based Payment Arrangement, Expense, Tax Benefit Payment period for vested share credits Payment Period For Vested Share Credits Period over which vested share credits will be paid upon separation from service. Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Interest payments due thereafter Long-Term Debt, Repayments Of Interest After Year Five Long-Term Debt, Repayments Of Interest After Year Five Plan assets Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets Total deferred tax liabilities Deferred Tax Liabilities, Gross Percentage of employer matching contribution of employee contributions Defined Contribution Plan, Employer Matching Contribution, Percent of Match Collections on agent loans Proceeds from Collection of Loans Receivable Share Repurchase Program [Axis] Share Repurchase Program [Axis] Total available-for-sale securities Available-For-Sale Debt Securities, Impairment (Loss) Recovery Available-For-Sale Debt Securities, Impairment (Loss) Recovery Income Statement [Abstract] Income Statement [Abstract] Entry Registrant Name Entity Registrant Name Maximum percentage of employee compensation that can be deferred Incentive Compensation, Maximum Annual Contributions Per Employee, Percent Maximum percentage of employee compensation the employee may defer under a deferred compensation plan of the Company. Exchange Home Office Properties Exchange Home Office Properties [Member] Exchange Home Office Properties Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Axis] Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Axis] Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Axis] Other, net Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Income tax expense Income tax expense Income Tax Expense (Benefit) 2024 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Receivables from Erie Insurance Exchange and affiliates, net Accounts Receivable, after Allowance for Credit Loss, Current Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Entity Tax Identification Number Entity Tax Identification Number Fair value of plan assets: Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Schedule Of Earnings Per Share Basic And Diluted [Table] Schedule Of Earnings Per Share Basic And Diluted [Table] Disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. Employee savings plan Schedule of Defined Contribution Plans Disclosures [Line Items] [Line Items] for Schedule of Defined Contribution Plans Disclosures [Table] Investment Type [Axis] Investment Type [Axis] Document Fiscal Period Focus Document Fiscal Period Focus Assumed conversion of Class B shares Dilutive Securities Effect on Basic Earnings Per Share Assumed Conversion [Abstract] -- None. No documentation exists for this element. -- Agent bonuses AgentBonusesPayableCurrent Carrying value as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to independent agents or earned by them based on the terms of one or more relevant arrangements. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Total current assets Assets, Current Financial services sector Financial Services Sector [Member] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Transferred over time Transferred over Time [Member] Estimated fair value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Current portion of long-term borrowings Long-term Debt, Current Maturities Total payments due in 2025 Long-Term Debt, Repayments Of Principal and Interest In Year Four Long-Term Debt, Repayments Of Principal and Interest In Year Four Investments by Secondary Categorization [Domain] Investments by Secondary Categorization [Domain] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Retirement Plan Funding Status [Domain] Defined Benefit Plan, Funding Status [Domain] Equity Component [Domain] Equity Component [Domain] Prepaid expenses Deferred Tax Liabilities, Prepaid Expenses Agent Bonus [Axis] Agent Bonus [Axis] Agent Bonus [Axis] Number of new plan participants resulting in charges recognized as amendments Defined Benefit Plan Number of New Plan Participants Related to Amendments The number of new plan participants for which amendment charges were recognized. OCI (loss) before reclassifications Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category [Axis] Consumer sector Consumer Sector [Member] Consumer Sector Available-for-sale securities, net Debt Securities, Available-for-sale, Noncurrent Class B common stock - basic and diluted (in dollars per share) Earnings Per Share, Basic and Diluted Schedule of Fair Value Measurements of Pension Plan Assets by Major Category and Level of Input Schedule of Allocation of Plan Assets [Table Text Block] Schedule of Property, Plant and Equipment and Finite-Lived Intangible Assets, Net by Type [Table] Schedule of Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Table] Schedule of Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Table] Unrealized losses on investments Deferred Tax Asset, Debt Securities, Available-for-Sale, Unrealized Loss Equity securities Payments to Acquire Marketable Securities Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Level 2 Level 2 Fair Value, Inputs, Level 2 [Member] Pension and other postretirement plans, OCI (loss) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent Type of Adoption [Domain] Accounting Standards Update [Domain] Contract liability Contract with Customer, Liability, Noncurrent Auditor Location Auditor Location Number of classes of common stock Number Of Classes Of Common Stock Number Of Classes Of Common Stock Total Debt Securities, Available-for-sale, Unrealized Loss Position Service agreement revenue received Proceeds from Fees Received Amortized cost Debt Securities, Available-for-sale, Amortized Cost Estimated useful life Finite-Lived Intangible Asset, Useful Life Long-term incentive plan awards Allocated Share-based Compensation Expense, Gross Represents the gross expense, before forfeitures, 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. Incentive Plan by Performance Period [Axis] Incentive Plan by Performance Period [Axis] Information pertaining to the entity's incentive plans, by the period over which performance is measured to determine the award. Use of estimates Use of Estimates, Policy [Policy Text Block] Schedule of Reconciliation of the Numerators and Denominators Used in the Basic and Diluted Per-Share Computations Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Total other comprehensive income, net of tax Other comprehensive income OCI (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Title of 12(b) Security Title of 12(b) Security Common stock, authorized (in shares) Common Stock, Shares Authorized Average price per share for shares purchased (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Per Share Weighted Average Price of Shares Purchased Incentive Plan Performance Period [Domain] Incentive Plan Performance Period [Domain] Identification of the period over which performance is measured to determine awards under the entity's incentive plans. Uncertain tax position, impact of settlement on effective tax rate Effective Income Tax Rate Reconciliation, Tax Settlement, Percent Allocated net income (numerator) Net Income (Loss) Available to Common Stockholders, Basic Document Type Document Type Retirement Plan Tax Status [Axis] Retirement Plan Tax Status [Axis] Product and Service [Domain] Product and Service [Domain] Total plan awards and earnings Incentive Plans and Deferred Compensation Total Awards and Earnings The amount of expense recognized in income during the period arising from cash-based incentives, share/equity-based compensation plans, and deferred compensation arrangements, with employees, directors and potentially certain consultants qualifying for treatment as employees. Maximum letter of credit sublimit under the bank revolving line of credit Letters Of Credit Maximum, Amount The maximum letters of credit capacity under the credit facility as of the reporting date. Fixed interest rate of credit facility Debt Instrument, Interest Rate, Stated Percentage Realized investment gains Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Number of deferred compensation plans for executives, senior vice presidents and other selected officers Number of Executive Deferred Compensation Plans Represents the Company's number of deferred compensation plans for executives, senior vice presidents and other selected officers. Decrease in unrecognized tax benefits Tax expense related to uncertain tax positions Unrecognized Tax Benefits, Period Increase (Decrease) Revolving Line of Credit Revolving Credit Facility [Member] Plan assets Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets Measurement Frequency [Axis] Measurement Frequency [Axis] Realized investment gains Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Administrative services reimbursements received Administrative Services Reimbursements Received Administrative Services Reimbursements Received Postretirement annual benefit expense reimbursed to Indemnity from the exchange and its subsidiaries Defined Benefit Plan, Postretirement Benefit (Expenses) Reimbursement Percentage Represents the percentage at which postretirement benefit expenses are reimbursed to the attorney-in-fact. Amortized cost Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Agent Bonus [Domain] Agent Bonus [Domain] [Domain] for Agent Bonus [Axis] Vesting [Domain] Vesting [Domain] Equity securities Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract] Subsequent Events Subsequent Events [Text Block] Amortization of prior service cost Amortization of prior service costs Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Weighted average shares outstanding – Diluted Weighted Average Number of Shares Outstanding, Diluted [Abstract] Related party transactions Related Party Transaction [Line Items] Vesting period of performance and/or service condition(s) Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Equity in (losses) earnings of limited partnerships Income (Loss) from Equity Method Investments Fair Value Fair Value Disclosures [Text Block] Lease amortization expense Lease Amortization Expense Amount of amortization of right of use asset. Minimum number of insurer affiliates to be classified as an insurance holding company system Insurance Holding Company System, Minimum Affiliate Insurers Minimum number of insurer affiliates to be defined as an insurance holding company system. Benefits expected to be paid over the next 10 years from pension plans: Defined Benefit Plan, Expected Future Benefit Payment [Abstract] Increase (decrease) in accrued agent bonuses Increase Decrease In Accrued Agent Bonuses The increase (decrease) during the reporting period in the aggregate amount of bonus obligations related to services received from independent agents. Administrative services expenses paid Administrative Services Expenses Paid Administrative Services Expenses Paid Deferred tax liabilities: Deferred Tax Liabilities, Gross [Abstract] Available-for-sale securities Available-for-sale Securities [Member] Impairment (recoveries) losses Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Tax Depreciation and amortization Depreciation, Depletion and Amortization and Gain (Loss) on Disposition The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets and the amount of gain (loss) on sale or disposal of property, plant and equipment assets, excluding oil and gas property and timber property. Performance Period Long Term Incentive Plan 2017-2019 Performance Period Long Term Incentive Plan 2017 To 2019 [Member] Represents the 2016-2018 performance period under the entity's Long-Term Incentive Plan. Operating revenue Revenues [Abstract] Interest payments due in 2026 Long-Term Debt, Repayments Of Interest In Year Five Long-Term Debt, Repayments Of Interest In Year Five Document Period End Date Document Period End Date Impairment (recoveries) losses Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax Incentive plan compensation cost reimbursed to Indemnity from the exchange and its subsidiaries Incentive Plans, Compensation Cost Reimbursement Percentage Represents the percentage at which incentive plan costs are reimbursed to the parent company. U.S. equity securities Us Equity Securities [Member] Ownership interest or right to acquire or dispose of ownership interest in corporations and other legal entities in the United States for which ownership interest is represented by shares of common or preferred stock, convertible securities, stock rights, or stock warrants. Funding of rabbi trust Deferred Compensation Equity Rabbi Trust Value of stock issued under share-based plans which is the unearned portion, accounted for under the fair value method. Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Accrued investment income Accrued Investment Income Receivable Repayment period of credit facility Debt Instrument, Term Equity compensation plan Equity Compensation Plan [Member] Represents the entity's equity compensation plan, which is designed to reward key employees, as determined by the entity's compensation committee or the chief executive officer, who can have a significant impact on the entity's long-term performance and to further align the interests of such employees with those of the entity's shareholders. The equity compensation plan permits grants of restricted shares, restricted share units and other share based awards, to be satisfied with shares of the entity's Class A common stock or cash. Amortization of prior service costs Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Total Investments, Fair Value Disclosure Total operating expenses Operating Expenses Actual asset allocation for the portfolio: Defined Benefit Plan, Information about Plan Assets [Abstract] OCI (loss) before reclassifications Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax Included in other comprehensive income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Total payments due in 2023 Long-Term Debt, Repayments Of Principal and Interest In Year Two Long-Term Debt, Repayments Of Principal and Interest In Year Two Earnings Per Share Earnings Per Share [Abstract] Funding target (as a percentage of the funding target liability) Defined Benefit Plan, Funding Target Percentage Plan assets of a defined benefit plan, as a percentage of the funding target liability as defined by the Pension Protection Act of 2006. Miscellaneous Gain (Loss) on Sale of Other Investments Tangible fixed assets, gross Property, Plant and Equipment, Gross Receivables from Erie Insurance Exchange, allowance for credit loss Accounts Receivable, Allowance for Credit Loss Net unrealized (losses) gains recognized on securities held at reporting date Equity Securities, FV-NI, Unrealized Gain (Loss) Treasury stock, at cost; 22,110,132 shares held Treasury Stock, Common, Value Management fee revenue - administrative services Administrative Services Management Fee [Member] Administrative services provided by Indemnity acting as attorney-in-fact on behalf of the Exchange, as well as a service provider for its insurance subsidiaries, with respect to all claims handling, life insurance, and investment management services. Asset acquisition, consideration transferred Asset Acquisition, Consideration Transferred Other Commitments [Line Items] Other Commitments [Line Items] Incentive compensation deferral plan Incentive Compensation Deferral Plan [Member] Represents the entity's incentive compensation deferral plan, which is a plan where participants can defer up to 100% of their annual or long-term incentive plan award. Deferred awards are credited to deferred stock account as credits denominated in Class A shares of the Company stock. No. of holdings Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Investment grade External Credit Rating, Investment Grade [Member] Asset Acquisition [Domain] Asset Acquisition [Domain] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Fixed Assets by Category Schedule of Property Plant and Equipment and Finite-Lived Intangible Assets, Net [Table Text Block] Schedule of Property Plant and Equipment and Finite-Lived Intangible Assets, Net Entity Current Reporting Status Entity Current Reporting Status Fair value of plan assets, beginning of year Fair value of plan assets, end of year Total  Defined Benefit Plan, Plan Assets, Amount Other debt securities Other Debt Obligations [Member] Equity securities Proceeds from Sale and Maturity of Marketable Securities Three Month Vesting Period Three Month Vesting Period [Member] For the entity's stock compensation plan for outside directors, each director vests in the grant 25% every three months over the course of a year. Third-Party Bank Third-Party Bank [Member] Third-Party Bank Schedule of Incentive Plans and Deferred Compensation [Table] Schedule of Incentive Plans and Deferred Compensation [Table] Schedule of awards, payments, deferrals and liabilities under the entity's incentive and deferred compensation plans. Pension and other postretirement plans, OCI (loss) Other Comprehensive (Income) Loss, Defined Benefit Plan, before Tax, after Reclassification Adjustment, Attributable to Parent Deferred taxes Income Tax, Policy [Policy Text Block] Changes in accumulated other comprehensive income (loss) by component, including amounts reclassified to other comprehensive income (loss) and the related line item in the Statements of Operations where net income is presented Accumulated Other Comprehensive Income (Loss) [Line Items] Qualified Plan Qualified Plan [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Utilities sector Utilities Sector [Member] Sector of the economy consisting of companies engaged in utilities. Recognition of management fee revenue and Recognition of service agreement revenue Revenue from Contract with Customer [Policy Text Block] Proceeds from investments: Proceeds from Sale, Maturity and Collection of Investments [Abstract] Common stock - diluted (in shares) Weighted shares (denominator) (in shares) Weighted Average Number of Shares Outstanding, Diluted Income Taxes Income Tax Disclosure [Text Block] Stock compensation plan for outside directors Stock Compensation Plan Outside Directors [Member] Represents the entity's stock compensation plan for outside directors, which is a plan to further align the interests of the directors with those of the entity's shareholders that provides for a portion of the directors' annual compensation in shares of the entity's Class A common stock. Upon ending board service, directors are paid shares of our Class A common stock equal to the number of share credits in their deferred stock account. Weighted average shares outstanding – Basic Weighted Average Number of Shares Outstanding, Basic [Abstract] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Related Party [Domain] Related Party [Domain] Transferred at point in time Transferred at Point in Time [Member] Schedule of Cost of Pension Plans Schedule of Net Benefit Costs [Table Text Block] Allowance for management fee returned on cancelled policies Deferred Tax Assets, Net Allowance for Premium Cancellations The amount as of the balance sheet date of the estimated future tax effects attributable to the difference between the methods used to account for the allowance for premium cancellations for tax purposes and under generally accepted accounting principles. The difference in basis of such prepaid expenses will reduce future taxable income when such basis difference reverses. Other assets Other Assets [Policy Text Block] Disclosure of accounting policy for other assets, including operating lease assets, limited partnerships and other long-term prepaid assets. Stock repurchase program Share Repurchase Program 1999 [Member] A stock repurchase program was authorized by the company's board of directors for the purchase of its outstanding Class A nonvoting common stock beginning January 1, 1999. These shares are recorded as Treasury shares in the company's statements of financial position at total cost based upon trade date. Less: investment expenses Investment Income, Investment Expense Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Common stock Class of Stock [Line Items] Credit Facility [Axis] Credit Facility [Axis] Entity Address, Address Line One Entity Address, Address Line One Schedule of Amounts Recognized in Other Comprehensive Income for Pension Plans Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Change in unrealized holding (losses) gains on available-for-sale securities Investment securities, OCI (loss) Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Total investment income Interest and Dividend Income, Operating and Income (Loss) from Equity Method Investments Entity Shell Company Entity Shell Company Total current liabilities Liabilities, Current Increase (decrease) in commissions payable Increase (Decrease) in Reserve for Commissions, Expense and Taxes Cash equivalents and other Cash Equivalents and Other [Member] Cash Equivalents and Other Administrative services Administrative Services [Policy Text Block] Disclosure of accounting policy for administrative services provided by Indemnity acting as attorney-in-fact on behalf of the Exchange, as well as a service provider for its insurance subsidiaries, with respect to all claims handling, life insurance, and investment management services. Interest payments due in 2022 Long-Term Debt, Repayments Of Interest In Year One Long-Term Debt, Repayments Of Interest In Year One Other Money Market Funds [Member] Percentage of eligible employee compensation, matched by employer Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Schedule of Defined Benefit Pension Plans with Projected Benefit Obligations in Excess of Plan Assets Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block] Current Fiscal Year End Date Current Fiscal Year End Date Participation amount in loan program Financing Receivable, before Allowance for Credit Loss Nonqualified Plan Nonqualified Plan [Member] Commissions payable Accrued Sales Commission, Current Administrative services reimbursement revenue Administrative Services Reimbursements [Member] Administrative services expenses, which are expenses incurred by Indemnity acting as attorney-in-fact on behalf of the Exchange, as well as a service provider for its insurance subsidiaries, with respect to all claims handling, life insurance, and investment management services. Statement [Table] Statement [Table] Schedule of Investment Income, Net of Expenses, from Portfolios Investment Income [Table Text Block] Accumulated benefit obligation Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation Recently adopted accounting standards New Accounting Pronouncements, Policy [Policy Text Block] Other Deferred Tax Assets, Other Available amount of letters of credit sublimit under the bank revolving line of credit Letters Of Credit Available, Amount The available amount of letters of credit less the amount of the contingent obligation under letters of credit outstanding under the credit facility as of the reporting date. 2026 Defined Benefit Plan, Expected Future Benefit Payment, Year Five Non-investment grade External Credit Rating, Non Investment Grade [Member] Total unrecognized compensation cost related to share-based compensation plan awards pertaining to open performance periods Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Statistical Measurement [Axis] Statistical Measurement [Axis] Roll forward of level 3 fair value measurements on a recurring basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Number of incentive plans for executives, senior vice presidents and other selected officers Number of Executive Incentive Plans Represents the Company's number of incentive plans for executives, senior vice presidents and other selected officers. Total payments due in 2026 Long-Term Debt, Repayments Of Principal and Interest In Year Five Long-Term Debt, Repayments Of Principal and Interest In Year Five Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Post-retirement discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation Post Retirement, Discount Rate The post-retirement interest rate used to adjust for the time value of money for the plan. Scenario [Domain] Scenario [Domain] Impairment (recoveries) losses Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax Related Party Related Party Transactions Disclosure [Text Block] Pension and other postretirement plans: Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Number of deferred compensation plans for outside directors Number of Director Deferred Compensation Plans Represents the Company's number of deferred compensation plans for directors. Investment income from portfolios Net Investment Income [Line Items] 12 months or longer Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Administrative services Administrative Services [Member] Revenue allocated to administrative services, which includes two components: (1) management fee revenue allocated to the administrative services Indemnity provides acting as attorney-in-fact on behalf of the Exchange and its property and casualty insurance subsidiaries with respect to all claims handling and investment management services, as well as the service provider for all life insurance and investment management services for Erie Family Life Insurance Company; and (2) the revenue recorded for the reimbursement of the administrative services expenses. Deferred income tax (benefit) expense Deferred income tax (benefit) expense Deferred Income Tax Expense (Benefit) Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Domain] Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Domain] Property, Plant and Equipment and Finite-Lived Intangible Assets, Net By Type [Domain] Amount of authorized stock repurchases approved for continuation under the current program Stock Repurchase Program, Authorized Amount Asset Acquisition [Axis] Asset Acquisition [Axis] Earnings per share Earnings Per Share, Policy [Policy Text Block] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Net income Net income Net Income (Loss) Attributable to Parent Expense Classification [Domain] Expense Classification [Domain] Represents the nature and type of expenses. Interest cost on benefit obligation Defined Benefit Plan, Interest Cost Statistical Measurement [Domain] Statistical Measurement [Domain] Schedule of Future Principal Payments Schedule of Maturities of Long-term Debt [Table Text Block] Deferred compensation plans and stock compensation plan for outside directors Deferred Compensation Plan And Stock Compensation Plan Outside Directors [Member] Represents the entity's combined deferred compensation plans and stock compensation plan for outside directors. The entity's deferred compensation plans, which are arrangements for the entity's executive and senior vice presidents and outside directors that allows participants to elect to defer receipt of a portion of their compensation until a later date. The deferred compensation plan for the entity's outside directors allows participants to defer receipt of a portion of their director and meeting fees until a later date. The entity's stock compensation plan for outside directors, which is a plan to further align the interests of the directors with those of the entity's shareholders that provides for a portion of the directors' annual compensation in shares of the entity's Class A common stock. Upon ending board service, directors are paid shares of our Class A common stock equal to the number of share credits in their deferred stock account. Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Additional paid-in-capital Additional Paid in Capital, Common Stock Other assets Other Assets, Noncurrent Liability incurred to purchase fixed assets Noncash or Part Noncash Acquisition, Fixed Assets Acquired Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Retirement Benefits [Abstract] Retirement Benefits [Abstract] Industrial sector Industrial Sector [Member] Industrial Sector Entity File Number Entity File Number Other investments Proceeds from Sale and Maturity of Other Investments Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Investments Investments in Debt and Equity Instruments, Cash and Cash Equivalents, Unrealized and Realized Gains (Losses) [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Dividends payable Dividends Payable, Current 50% employer matching contribution Fifty Percent Match [Member] A 50 percent match of the provided unit. Agent loans - expected credit recoveries (losses) Financing Receivable, Credit Loss, Expense (Reversal) Actual gain on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) OCI (loss) before reclassifications OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Available-for-sale securities maturities/calls Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Investment securities, OCI (loss) OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Other employee benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Other Share Repurchase Program [Domain] Share Repurchase Program [Domain] Credit Facility [Domain] Credit Facility [Domain] Assets Assets [Abstract] Administrative services Related Party Transactions [Abstract] Principal payments due in 2024 Long-Term Debt, Maturity, Year Three Period of prior year actual underwriting data used to estimate agent bonuses Agent Bonus Estimate Actual Underwriting Data, Period Represents the period of prior year actual underwriting data used to estimate agent bonuses. Accumulated Benefit Obligation in Excess of Plan Assets Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract] Schedule of Target and Actual Asset Allocations for the Portfolio Schedule of Target and Actual Allocations of Plan Assets [Table Text Block] Tabular disclosure of the target and actual allocations of the major categories of plan assets of pension plans and/or other employee benefit plans. Incentive and Deferred Compensation Plans Disclosure Of Compensation Related Costs, Cash Based Incentive And Share Based Payments And Deferred Compensation [Text Block] The entire disclosure for compensation-related costs for cash-based incentive and share/equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of compensation, incentive distributions, compensation arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details, employee stock purchase plan details, and income statement compensation items. Deferred compensation arrangements may include a description of an arrangement with an individual employee, which is generally an employment contract between the entity and a selected officer or key employee containing a promise by the employer to pay certain amounts at designated future dates, usually including a period after retirement, upon compliance with stipulated requirements. This type of arrangement is distinguished from broader based employee benefit plans as it is usually tailored to the employee. Disclosure also typically includes the amount of related compensation expense recognized during the reporting period, the number of shares (units) issued during the period under such arrangements, and the carrying amount as of the balance sheet date of the related liability. New Accounting Pronouncements or Change in Accounting Principle [Table] Accounting Standards Update and Change in Accounting Principle [Table] Purchase of investments: Payments to Acquire Investments [Abstract] Timing of Transfer of Good or Service [Axis] Timing of Transfer of Good or Service [Axis] Discount rate Discount rate used to measure future benefit obligations Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Decrease (increase) in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Increase in accrued investment income Increase (Decrease) in Accrued Investment Income Receivable Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Related Party [Axis] Related Party [Axis] Interest expense related to uncertain tax positions Unrecognized Tax Benefits, Interest on Income Taxes Expense Prior service cost amortization Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Secured Debt Secured Debt [Member] Equity securities Equity Securities, FV-NI, Total Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Operating lease assets obtained in exchange for new operating lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Schedule of Temporary Differences and Carry-Forwards, which Give Rise to Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Realized gains (losses) on investments Gain (Loss) on Securities [Line Items] Total investment income Investment Income, Nonoperating Vesting percent of the grant in Class A common stock Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage 100% employer matching contribution One Hundred Percent Match [Member] A 100 percent match of the provided unit. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Total plan assets Defined Benefit Plan, Plan Assets, Target Allocation, Percentage Net actuarial gain arising during the year Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax Allocated net income (numerator) Net Income (Loss) Attributable to Parent, Diluted Allocated net income (numerator) Dilutive Securities, Effect on Basic Earnings Per Share, Dilutive Convertible Securities Decrease in prepaid pension Increase (Decrease) in Prepaid Pension Increase (Decrease) in Prepaid Pension Gross realized losses Debt Securities, Available-for-sale, Realized Loss, Excluding Other-than-temporary Impairment Deferred compensation Common Stock Issued Director Stock Trust Value of common stock issued to a trust (for example, a 'rabbi trust') set up specifically to accumulate stock for the sole purpose of distribution to participating directors. This trust does not allow directors to immediately or after a holding period diversify into nonemployer securities. The deferred compensation plan for which this trust is set up must be settled by the delivery of a fixed number of shares of employer stock. Commitments and contingencies Commitments and Contingencies, Policy [Policy Text Block] Management fee received Proceeds from Insurance Agency Management Fees Received Cash received for management fees during the current period. Matching contributions reimbursed to Indemnity from the exchange and its subsidiaries Defined Contribution Plan, Matching Contributions Reimbursement Percentage Represents the percentage at which 401(k) matching contributions are reimbursed to the attorney-in-fact. Energy sector Energy Sector [Member] Sector of the economy consisting of companies engaged in energy. Collateralized debt obligations Collateralized Debt Obligations [Member] Schedule of Disaggregation of Revenue by Performance Obligation Disaggregation of Revenue [Table Text Block] Principal payments due in 2026 Long-Term Debt, Maturity, Year Five Employer matching contribution paid to the plan Defined Contribution Plan, Cost Unrealized gains on investments Deferred Tax Liabilities, Unrealized Gains on Investments Including Equity Method Investments Deferred Tax Liabilities, Unrealized Gains on Investments Including Equity Method Investments Minimum target normal cost threshold necessary for future pension funding Defined Benefit Plan, Target Normal Cost Threshold Minimum target normal cost threshold necessary for future pension funding. Nature of expense as a percentage of total policy issuance and renewal expenses Percentage of Total Expenses Represents the nature and type of expense as a percentage of total expenses. Net investment (income) loss Accretion (Amortization) of Discounts and Premiums, Investments and Income (Loss) from Equity Method Investments The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method. Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities. Lease expense on office space leased from exchange Operating Lease, Payments Maximum number of shares authorized for grant (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized U.S. small capitalization core equity Us Small Capitalization Core Equity [Member] This category includes U.S. equity securities that seek to achieve excess returns relative to the Russell 2000 Index while maintaining portfolio risk characteristics similar to the index. Less: Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment and Finite-Lived Intangible Assets Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services and intangible assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Commissions paid to agents Payments for Commissions Reconciliation of unrecognized tax benefits Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Projects in progress Software Development [Member] Non-U.S. equity securities Foreign Equity Securities [Member] Ownership interest or right to acquire or dispose of ownership interest in foreign corporations and other foreign legal entities for which ownership interest is represented by shares of common or preferred stock, convertible securities, stock rights, or stock warrants. Total liabilities and shareholders' equity Liabilities and Equity Investments, Debt and Equity Securities [Abstract] Contract liability Contract with Customer, Liability, Current Benefits paid Defined Benefit Plan, Plan Assets, Benefits Paid Long-term incentive plan awards Long Term Incentive Plan [Member] Represents the entity's long-term incentive plan, which is a performance based incentive plan designed to reward the entity's executive and senior vice presidents who can have a significant impact on the entity's long-term performance and to further align the interests of such employees with those of the entity's shareholders. The long-term incentive plan permits grants of performance shares or units, to be satisfied with shares of the entity's Class A common stock or cash payment as determined by the compensation committee. Deferred compensation Deferred Compensation Under Rabbi Trust Plans Deferred compensation under rabbi trust plans that represents the value of common stock issued to the rabbi trust set up specifically to accumulate stock for the sole purpose of distribution to participants, which is part of stockholders' equity. Concentration Risk [Line Items] Concentration Risk [Line Items] Miscellaneous Miscellaneous Investments [Member] Cash flows from operating activities Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Earnings Per Share Earnings Per Share [Text Block] Timing of Transfer of Good or Service [Domain] Timing of Transfer of Good or Service [Domain] Operating expenses Operating Expenses [Abstract] Retirement Plan Funding Status [Axis] Defined Benefit Plan, Funding Status [Axis] 2023 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Minimum Minimum [Member] Fixed assets Property Plant And Equipment and Finite-Lived Intangible Assets, Net By Type [Abstract] Property Plant And Equipment and Finite-Lived Intangible Assets, Net By Type [Abstract] Loan Purchase Commitments Loan Purchase Commitments [Member] Borrowings outstanding under the bank revolving line of credit Long-term Line of Credit Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Proceeds from disposal of fixed assets Proceeds from Sale of Productive Assets Performance Period Long Term Incentive Plan 2019-2021 Performance Period Long Term Incentive Plan 2019 To 2021 [Member] Performance Period Long Term Incentive Plan 2019 To 2021 Due after ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Auditor Information [Abstract] Auditor Information Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] 12 months or longer Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Principal payments due in 2025 Long-Term Debt, Maturity, Year Four Supplementary Data on Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Borrowing Arrangements Debt Disclosure [Text Block] Net amount recognized in the Statements of Financial Position: Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract] Schedule of Provision for Income Taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Level 3 Level 3 Fair Value, Inputs, Level 3 [Member] Dividends paid to shareholders Payments of Ordinary Dividends, Common Stock Minimum number of affiliates to be classified as an insurance holding company system Insurance Holding Company System, Minimum Affiliates Minimum number of affiliates to be defined as an insurance holding company system. International emerging markets equity Emerging Markets Equity [Member] This category seeks long-term capital growth in securities of companies that have their principal business activities in countries in the Morgan Stanley Capital International Emerging Markets Free Index. Erie Insurance Exchange (EIE) Erie Insurance Exchange [Member] Represents Erie Insurance Exchange, a Pennsylvania-domiciled reciprocal insurer that writes property and casualty insurance. Class A common stock held by plan participants (in shares) Defined Contribution Plan Number of Equity Securities Issued by Employer and Related Parties Included in Plan Assets The number of employer shares or related party shares included in the defined contribution plan assets. Outstanding amount of letters of credit sublimit under the bank revolving line of credit Letters of Credit Outstanding, Amount Performance Period Long-Term Incentive Plan 2018-2020 Performance Period Long Term Incentive Plan 2018 To 20120 [Member] Represents the 2017-2019 performance period under the entity's Long-Term Incentive Plan. Disaggregation of revenue by performance obligation Disaggregation of Revenue [Line Items] Basis of presentation Basis of Accounting, Policy [Policy Text Block] Performance shares Performance Shares [Member] Accumulated other comprehensive loss AOCI (loss), beginning of year AOCI (loss), end of year Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Emerging Growth Company Entity Emerging Growth Company Class of Treasury Stock [Table] Class of Treasury Stock [Table] Capital Stock Stock by Class [Text Block] The entire disclosure of an entity's stock (includes common, convertible, and preferred stocks), including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock including , and, the entire disclosure for an entity's treasury stock, including the average cost per share, carrying basis for each class of treasury stock, description of share repurchase program authorized by an entity's board of directors, the number of shares repurchased, the cost of the shares repurchased, the remaining maximum dollar value of shares available for repurchase under the program, the treatment of the purchase price in excess of the current market value, number of shares held for each class of treasury stock and other information necessary to a fair presentation, and EPS information. Performance Period Long-Term Incentive Plan 2016-2018 Performance Period Long Term Incentive Plan 2016 To 2018 [Member] Represents the 2015-2017 performance period under the entity's Long-Term Incentive Plan. Retirement Plan Tax Status [Domain] Retirement Plan Tax Status [Domain] OCI (loss) before reclassifications Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax Accounting Standards Update 2016-13 Accounting Standards Update 2016-13 [Member] Auditor Name Auditor Name Cover [Abstract] Cover [Abstract] Cash and cash equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Schedule of Available-For-Sale Securities in a Gross Unrealized Loss Position by Length of Time Schedule of Unrealized Loss on Investments [Table Text Block] Compensation increases Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Receivables from Erie Insurance Exchange and its affiliates Accounts Receivable, Related Parties, Current Schedule of Amounts Included in Accumulated Other Comprehensive Loss that were Not Yet Recognized as Components of Net Benefit Costs Schedule of Net Periodic Benefit Cost Not yet Recognized [Table Text Block] Shares purchased for share-based compensation awards (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award OCI (loss) before reclassifications OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Financial Instrument [Axis] Financial Instrument [Axis] Interest payments due in 2025 Long-Term Debt, Repayments Of Interest In Year Four Long-Term Debt, Repayments Of Interest In Year Four Percentage of dividend declared on Class B common stock used to determine dividend payable on Class A common stock Dividends Common Stock Percentage Represents the percentage of the dividend declared on Class B common stock to which a multiplier is applied to determine the required dividend on Class A common stock. Investment securities, OCI (loss) Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent Carrying Value Reported Value Measurement [Member] Total fixed assets, gross Finite Lived Intangible Assets And Property Plant And Equipment Gross Amount before amortization, accumulated depreciation and depletion, of assets, excluding financial assets and goodwill, lacking physical substance with a finite life and physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, capitalized internally developed software, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. Common stock Common Stock [Member] Operating income Operating Income (Loss) Amounts included in accumulated other comprehensive loss Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract] Fair value of financial instruments, transfers between levels Fair Value Transfer, Policy [Policy Text Block] Gross unrealized losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Weighted shares (denominator) (in shares) Incremental Common Shares Attributable to Conversion of Convertible Common Stock Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible common stock using the if-converted method. Treasury stock (in shares) Treasury Stock, Common, Shares Net realized gains on available-for-sale securities Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment Accumulated other comprehensive income (loss), net of tax AOCI Attributable to Parent, Net of Tax [Roll Forward] Net realized investment gains (losses) Realized Investment Gains (Losses) [Abstract] OCI (loss) Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Treasury stock Treasury Stock [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Deferred executive compensation Deferred Compensation Liability, Classified, Noncurrent Available-for-sale securities Payments to Acquire Debt Securities, Available-for-sale Credit recovered (impaired) Debt Securities, Available-for-sale, Change in Present Value, Expense (Reversal) Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid Equity securities Equity Securities, FV-NI, Noncurrent Fixed Assets Property, Plant, and Equipment and Intangible Assets [Text Block] Management fee revenue - policy issuance and renewal services Policy Issuance and Renewal Services [Member] Policy issuance and renewal services provided by Indemnity that result in executed insurance policies between the Exchange or one of its insurance subsidiaries and the subscriber (policyholder). Accumulated benefit obligation, end of year Defined Benefit Plan, Accumulated Benefit Obligation Employer contributions during fiscal year Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Deferred executive compensation, beginning of the year Deferred executive compensation, end of the year Accrued Bonuses And Deferred Compensation Liability, Current And Noncurrent The carrying amount of the liability as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to employees and directors or earned by them based on the terms of one or more relevant arrangements, and to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting from contractual terms or a death benefit. Realized investment gains Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Total liabilities Liabilities Salaries and wages paid Payments to Employees External Credit Rating by Grouping [Axis] External Credit Rating by Grouping [Axis] Ratio for converting shares of Class B common stock into shares of Class A common stock Ratio for converting shares of Class B common stock into shares of Class A common stock Common Stock Conversion Ratio The ratio applied to Class B common stock shares for purposes of determining the number of Class A common stock shares into which the stock will be converted (the number of Class A common stock shares into which one Class B common stock share may be converted). Common stock, issued (in shares) Common Stock, Shares, Issued Schedule of Reconciliation of Beginning and Ending Balances of the Fair Value of Plan Assets Schedule of Changes in Fair Value of Plan Assets [Table Text Block] Fair value of investments pledged as collateral on the bank revolving line of credit Security Owned and Pledged as Collateral, Fair Value Net amount not yet recognized Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Total recognized in other comprehensive income Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax Intent to sell Debt Securities, Available-for-sale, Sell before Recovery Debt Securities, Available-for-sale, Sell before Recovery Schedule of Actuarial Assumptions Used to Measure the Year-End Obligations and Net Periodic Benefit Costs for the Subsequent Year Defined Benefit Plan, Assumptions [Table Text Block] Entity Address, City or Town Entity Address, City or Town Schedule of Defined Benefit Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Table Text Block] Schedule of Benefits Expected to be Paid Over the Next 10 Years from Pension Plans Schedule of Expected Benefit Payments [Table Text Block] Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component, Including Amounts Reclassified to Other Comprehensive Income (Loss) and the Related Line item in the Statements of Operations Where Net Income is Presented Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Fair value Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] Supplemental disclosure of noncash transactions Noncash Investing and Financing Items [Abstract] Schedule of Unrecognized Tax Benefits Roll Forward Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Software Software and Software Development Costs [Member] Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Measurement Frequency [Domain] Measurement Frequency [Domain] Interest expense, net Interest Expense Schedule of Realized Gains and Losses on Investments and Net Unrealized Gains and Losses Recognized during the Reporting Period Related to Equity Securities Held at the Reporting Date Realized and Unrealized Gain (Loss) on Investments [Table Text Block] Tabular disclosure of realized and unrealized gains and losses on investments reported in the statement of income. Expected return on assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets Available-for-sale, equity securities, cash equivalents, and other Interest and Dividend Income, Operating 2022 Defined Benefit Plan, Expected Future Benefit Payment, Year One Retained earnings Retained Earnings (Accumulated Deficit) Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Entity Filer Category Entity Filer Category U.S. Treasury U.S. Treasury Strips US Treasury Securities [Member] Concentration Risk [Table] Concentration Risk [Table] Fair Value Estimate of Fair Value Measurement [Member] Amendment Flag Amendment Flag Funded Plan Defined Benefit Plan, Funded Plan [Member] Fair value of investments pledged as collateral on the credit facility Debt Instrument, Collateral Amount Equity Components [Axis] Equity Components [Axis] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Total plan assets Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage Fixed assets Schedule of Property, Plant and Equipment and Finite-Lived Intangible Assets, Net by Type [Line Items] [Line Items] for Schedule of Property, Plant and Equipment and Finite-Lived Intangible Assets, Net by Type [Table] Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Defined Contribution Plans [Axis] Defined Contribution Plans [Axis] Defined Contribution Plans [Axis] Fair value measurements on a recurring basis by asset class and level of input Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Product and Service [Axis] Product and Service [Axis] U.S. equity index Us Equity Index [Member] This category comprises U.S. equity index funds not actively managed that track the S&P 500. Public Float Entity Public Float Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Primary agent bonus Primary Agent Bonus [Member] Information related to the primary agent bonus plan. Investments [Abstract] Investments [Abstract] Statement Statement [Line Items] Carrying values and fair value measurements of financial instruments not carried at fair value Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] (Decrease) increase in contract liability Increase (Decrease) in Contract with Customer, Liability Total plan awards paid Incentive Plan Compensation Total Liabilities Paid The liabilities paid during the accounting period for cash-based incentive and share/equity-based compensation plans, with employees, directors, and potentially certain consultants qualifying for treatment as employees. (Gain) loss on disposal of fixed assets Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property External Credit Rating by Grouping [Domain] External Credit Rating by Grouping [Domain] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Available-for-sale securities Estimated fair value Estimated fair value Debt Securities, Available-for-sale Debt Disclosure [Abstract] Debt Disclosure [Abstract] Contractual Obligation, Fiscal Year Maturity Schedule [Abstract] Contractual Obligation, Fiscal Year Maturity Schedule [Abstract] Income available to stockholders on equivalent shares (Diluted EPS:) Net Income (Loss) Attributable to Parent, Diluted [Abstract] Maximum number of shares which may be received by any single participant during any specified period (in shares) Share Based Compensation Arrangement by Share Based Payment Award, Maximum Number of Shares Per Employee Per Specified Period 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. Deferred tax asset valuation allowance Deferred Tax Assets, Valuation Allowance Projected benefit obligation Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation Postretirement Benefits Retirement Benefits [Text Block] Document Annual Report Document Annual Report Forecast Forecast [Member] Vesting [Axis] Vesting [Axis] Total assets Assets Underwriting and policy processing expense Underwriting Expense [Member] Underwriting and policy processing services provided. Total plan Plan Name [Domain] Plan Name [Domain] Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activities Accumulated other comprehensive income (loss), tax AOCI Attributable to Parent, Tax [Abstract] AOCI Attributable to Parent, Tax [Abstract] Prior service cost Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax Post-retirement discount rate Defined Benefit Plan, Assumptions Used Calculating, Net Periodic Benefit Cost, Post Retirement Discount Rate The post-retirement interest rate used to adjust for the time value of money. General operating expenses paid Payments for Other Operating Activities Period of time over which management fee revenue allocated to administrative services will be recognized Period of time over which indemnity revenue will be recognized Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Net investment income received Proceeds from Interest and Dividends Received and Equity Method Investment Dividends or Distributions Cash received for dividends and interest on the entity's equity and debt investments during the current period and amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities. Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Furniture and fixtures Furniture and Fixtures [Member] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Common stock - basic (in shares) Weighted shares (denominator) (in shares) Weighted Average Number of Shares Outstanding, Basic Class A common stock - diluted (in dollars per share) Per- share amount (in dollars per share) Earnings Per Share, Diluted Information technology expense Information Technology Expense [Member] Information technology services that support all functions. Service cost for benefits earned Defined Benefit Plan, Service Cost Net actuarial loss Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Income taxes paid Income Taxes Paid, Net Accounting standards update Accounting Standards Update [Extensible Enumeration] Schedule of Impairments on Available-For-Sale Securities and Agent Loans Debt Securities, Available-for-sale, Allowance for Credit Loss [Table Text Block] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Forfeitures Compensation Arrangement with Individual, Forfeitures The amount of compensation forfeited by the individual during the period. Pension and other postretirement benefits Deferred Tax Assets, Tax Deferred Expense Compensation and Benefits Pensions and Postretirement Benefits The tax effect as of the balance sheet date of the amount of estimated future tax deductions arising from pension costs and postretirement benefits, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken. Realized (gains) and impairment (recoveries) losses on investments Realized Investment Gains (Losses) and Impairment of Investments The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, offset by the amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. Performance Period Equity Compensation Plan 2018 Performance Period Equity Compensation Plan 2018 [Member] Represents the 2016 performance period under the entity's Equity Compensation Plan. Corporate debt securities Corporate Debt Securities [Member] Schedule of Reconciliation of the Provision for Income Taxes, with Amounts Determined by Applying the Statutory Federal Income Tax Rate to Pre-Tax Income Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Projected Benefit Obligation in Excess of Plan Assets Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract] Depreciation and amortization expense Depreciation, Depletion and Amortization Transfer of investments from other investments to equity securities Transfer Between Investment Categories Value of investments transferred between the entity's investments in noncash transactions. Schedule of Fair Value Measurements on a Recurring Basis by Asset Class and Level of Input Fair Value, Assets Measured on Recurring Basis [Table Text Block] Accumulated other comprehensive (loss) income Total AOCI Attributable to Parent [Member] Common stock, outstanding (in shares) Common Stock, Shares, Outstanding Transfers into Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Financial Instruments [Domain] Financial Instruments [Domain] Due after five years through ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Nature of expense as a percentage of total policy issuance and renewal expenses Expense Classification [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Class B common stock Common Class B [Member] Accumulated other comprehensive income (loss), before tax AOCI Attributable to Parent [Abstract] Annual incentive plan awards Annual Incentive Plan [Member] Represents the entity's annual incentive plan, which is a bonus plan that pays cash to the entity's executive and senior vice presidents annually based upon attainment of corporate and individual performance measures, which can include various financial measures. Entity Central Index Key Entity Central Index Key Deferred tax assets: Deferred Tax Assets, Gross [Abstract] Maximum dollar amount which may be received by any single participant during any specified period Incentive Plan Maximum Compensation Expense Per Employee Per Specified Period The maximum amount of expense that may be earned by any single participant during any specified period, which may be a specified performance period or calendar year, arising from incentive plan compensation arrangements, other than share-based awards, with employees, directors and potentially certain consultants qualifying for treatment as employees. Total payments due in 2022 Long-Term Debt, Repayments Of Principal and Interest In Year One Long-Term Debt, Repayments Of Principal and Interest In Year One Reductions for prior year tax positions Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Due in one year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Agent bonus liability Commissions Expense, Policy [Policy Text Block] Communications sector Communications Sector [Member] Sector of the economy consisting of companies engaged in communications. Compensation Related Costs [Abstract] Compensation Related Costs [Abstract] Concentrations of Credit Risk Concentration Risk Disclosure [Text Block] Other long-term liabilities Other Liabilities, Noncurrent Unrealized losses Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] Residential mortgage-backed securities Residential Mortgage Backed Securities [Member] Projected benefit obligation, beginning of year Projected benefit obligation, end of year Defined Benefit Plan, Benefit Obligation Shares repurchased under stock repurchase program (in shares) Treasury Stock, Shares, Acquired Term loan credit facility Debt Instrument [Line Items] Debt Instrument [Line Items] Trading Symbol Trading Symbol Amortization of net actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax Other Deferred Tax Liabilities, Other Total Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Equipment Equipment [Member] Available borrowing capacity under the bank revolving line of credit, due to outstanding letters of credit Line of Credit Facility, Current Borrowing Capacity Line of Credit Facility [Table] Line of Credit Facility [Table] Available-for-sale securities sales Proceeds from Sale of Debt Securities, Available-for-sale Amortization of net actuarial loss Amortization of net actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Actuarial assumptions used to determine benefit obligations: Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Accounting Policies [Line Items] Accounting Policies [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Total payments due in 2024 Long-Term Debt, Repayments Of Principal and Interest In Year Three Long-Term Debt, Repayments Of Principal and Interest In Year Three (Decrease) increase in deferred compensation Increase (Decrease) in Deferred Compensation Revenue, Performance Obligation [Abstract] Revenue, Performance Obligation [Abstract] Long-term borrowings Long-term Debt, Excluding Current Maturities Compensation cost related to share-based compensation plan awards Share-based Payment Arrangement, Expense Net income per share Earnings Per Share, Basic and Diluted [Abstract] Projects in progress Finite-Lived Intangible Assets, Not Yet Subject To Amortization Amount of assets, excluding financial assets and goodwill, lacking physical substance with a finite life, that are not yet subject to amortization. Entities [Table] Entities [Table] Defined Contribution Plans [Domain] Defined Contribution Plans [Domain] [Domain] for Defined Contribution Plans [Axis] Investment Type Categorization [Domain] Investments [Domain] Class A common stock Common Class A [Member] Cash and cash equivalents Cash and cash equivalents, beginning of year Cash and cash equivalents, end of year Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Common stock, stated value per share (in dollars per share) Common Stock, Par or Stated Value Per Share Available-for-sales securities, allowance for credit loss Debt Securities, Available-for-sale, Allowance for Credit Loss Loan program, guaranteed amount Guarantor Obligations, Maximum Exposure, Undiscounted Postretirement benefits Fair value measurements of pension plan assets: Defined Benefit Plan Disclosure [Line Items] Current assets: Assets, Current [Abstract] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Intangible assets, gross Finite-Lived Intangible Assets, Gross OCI (loss) before reclassifications OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment and Tax Decrease (increase) in receivables from affiliates Increase (Decrease) in Accounts Receivable, Related Parties Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Fair Value, Measurements, Recurring Basis Fair Value, Recurring [Member] Incentive and deferred compensation plans Incentive Plans and Deferred Compensation [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Measurement Basis [Axis] Measurement Basis [Axis] Employer match and hypothetical earnings on deferred compensation Deferred Compensation Arrangement with Individual, Compensation Expense Fair value of financial instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Available-for-sale securities: Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment [Abstract] Auditor Firm ID Auditor Firm ID Net payments on long-term borrowings Proceeds from (Repayments of) Secured Debt Pre-retirement discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation Pre Retirement Discount Rate The pre-retirement interest rate used to adjust for the time value of money for the plan. Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Projected benefit obligation: Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Buildings and building improvements Building and Building Improvements [Member] Agents bonuses paid Payments For Agent Bonuses The amount of cash paid for agent bonuses during the current period. Class of Stock [Domain] Class of Stock [Domain] Schedule of Reconciliation of Beginning and Ending Balances of the Projected Benefit Obligation, as well as the Accumulated Benefit Obligation Schedule of Accumulated and Projected Benefit Obligations [Table Text Block] Maximum borrowing capacity under the bank revolving line of credit Line of Credit Facility, Maximum Borrowing Capacity Discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Bank line of credit Line of Credit Facility [Line Items] Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Net amount recognized Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position Dilutive effect of stock-based awards Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Allocated net income (numerator) Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units Income tax at statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Agent loans, allowance for credit loss Financing Receivable, Allowance for Credit Loss Due after ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Nature of Operations Nature of Operations [Text Block] Employee pension plan Pension Plan [Member] Due in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Fixed assets Fixed Assets [Policy Text Block] Disclosure of accounting policy for long-lived, physical assets used in the normal conduct of business and not intended for resale, and costs incurred for software when both (1) the software is acquired, internally developed, or modified solely to meet the entity's internal needs, and (2) during the software's development or modification, no substantive plan exists or is being developed to market the software externally. Includes, but is not limited to, basis of assets, depreciation, amortization and depletion methods used, including composite deprecation, estimated useful lives, capitalization policy, accounting treatment for costs incurred for repairs and maintenance, capitalized interest and the method it is calculated, disposals and impairments. Deferred executive compensation liability Incentive Plans And Deferred Compensation [Roll Forward] A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Adjustments to reconcile net income to net cash provided by operating activities: Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]