Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2019
Summary of Significant Accounting Policies [Abstract]
Description of Business	Description of Business: Protective Insurance Corporation (the "Company"), based in Carmel, Indiana, is a property-casualty insurer specializing in marketing and underwriting property, liability and workers' compensation coverage for trucking and public transportation fleets, as well as coverage for trucking industry independent contractors. In addition, the Company offers workers' compensation coverage for a variety of operations outside the transportation industry. The Company operates as one reportable property and casualty insurance segment, offering a range of products and services, the most significant being commercial automobile and workers' compensation insurance products. The term “Insurance Subsidiaries,” as used throughout this document, refers to Protective Insurance Company, Protective Specialty Insurance Company, Sagamore Insurance Company and B&L Insurance, Ltd.
Basis of Presentation	Basis of Presentation: The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and do not include all of the information and notes required by U.S. generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for fair presentation have been included. Interim financial statements should be read in conjunction with the Company's annual audited financial statements and other disclosures included in the Company's most recent Annual Report on Form 10-K. Operating results for interim periods are not necessarily indicative of results that may be expected for the year ending December 31, 2019 or any other future period.
Investments	Investments: Carrying amounts for fixed income securities represent fair value and are based on quoted market prices, where available, or broker/dealer quotes for specific securities where quoted market prices are not available. Equity securities are carried at quoted market prices (fair value). Commercial mortgage loans are carried primarily at amortized cost along with a valuation allowance for losses when necessary. These investments represent interests in commercial mortgage loans originated and serviced by a third party of which the Company shares, on a pro-rata basis, in all related cash flows of the underlying mortgage loans. There was no valuation allowance on the Company's commercial mortgage loans as of March 31, 2019. The Company accounts for investments in limited partnerships using the equity method of accounting, which requires an investor in a limited partnership to record its proportionate share of the limited partnership's net income. To the extent the limited partnerships include both realized and unrealized investment gains or losses in the determination of net income or loss, then the Company would also recognize, through its condensed consolidated statements of operations, its proportionate share of the investee's unrealized, as well as realized, investment gains or losses within net unrealized gains (losses) on equity securities and limited partnership investments. Short-term and other investments are carried at cost, which approximates their fair values. Fixed income securities are considered to be available-for-sale. The related unrealized net gains or losses (net of applicable tax effects) on fixed income securities are reflected directly in shareholders' equity. Included within available-for-sale fixed income securities are convertible debt securities. A portion of the changes in the fair values of convertible debt securities is reflected as a component of net realized gains (losses) on investments, excluding impairment losses within the condensed consolidated statements of operations. Realized gains and losses on disposals of fixed income securities are recorded on the trade date. Realized gains and losses on fixed income securities are determined by the specific identification of the cost of investments sold and are included in net realized gains (losses) on investments, excluding impairment losses. Effective January 1, 2018, equity securities are recorded at fair value, with unrealized net gains or losses reflected as a component of net unrealized gains (losses) on equity securities and limited partnership investments within the condensed consolidated statements of operations. Realized gains and losses on disposals of equity securities are recorded on the trade date and included in net realized gains (losses) on investments, excluding impairment losses. Prior to adoption of the new accounting guidance, unrealized gains and losses related to equity securities were reflected directly in shareholders’ equity unless a decline in value was determined to be other-than-temporary, in which case the loss was charged to income. In accordance with the Financial Accounting Standards Board's ("FASB") other-than-temporary impairment guidance, if a fixed income security is in an unrealized loss position and the Company has the intent to sell the fixed income security, or it is more likely than not that the Company will have to sell the fixed income security before recovery of its amortized cost basis, the decline in value is deemed to be other-than-temporary and is recorded to other-than-temporary impairment losses on investments in the condensed consolidated statements of operations. For impaired fixed income securities that the Company does not intend to sell or in cases where it is more likely than not that the Company will not have to sell such securities, but the Company expects that it will not fully recover the amortized cost basis, the credit component of the other-than-temporary impairment is recognized in other-than-temporary impairment losses on investments in the condensed consolidated statements of operations and the non-credit component of the other-than-temporary impairment is recognized directly in shareholders' equity. The credit component of an other-than-temporary impairment is determined by comparing the net present value of projected future cash flows with the amortized cost basis of the fixed income security. The net present value is calculated by discounting the Company's best estimate of projected future cash flows at the appropriate effective interest rate.
Recognition of Revenue and Costs	Recognition of Revenue and Costs: Premiums are earned over the period for which insurance protection is provided. A reserve for unearned premiums, computed by the daily pro-rata method, is established to reflect amounts applicable to subsequent accounting periods. Commissions to unaffiliated companies and premium taxes applicable to unearned premiums are deferred and expensed as the related premiums are earned. The Company does not defer acquisition costs that are not directly variable with the production of premium. If it is determined that expected losses and deferred expenses will likely exceed the related unearned premiums, the asset representing deferred policy acquisition costs is reduced and an expense is charged against current operations to reflect any such premium deficiency. In the event that the expected premium deficiency exceeds deferred policy acquisition costs, an additional liability would be recorded with a corresponding expense to current operations for the amount of the excess premium deficiency. Anticipated investment income is considered in determining recoverability of deferred acquisition costs. The Company had no material contract assets, contract liabilities, or deferred contract costs recorded on its condensed consolidated balance sheet at March 31, 2019.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements: In February 2016, the FASB issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842), or ASU 2016-02. ASU 2016-02 superseded the current lease guidance in Accounting Standards Codification ("ASC") Topic 840, Leases. Under the new guidance, lessees are required to recognize for all leases, with the exception of short-term leases, a lease liability, which is a lessee's obligation to make lease payments arising from a lease, measured on a discounted basis. Concurrently, lessees are required to recognize a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. The guidance provides for a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative periods presented in the financial statements. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements, or ASU 2018-11, which provided adopters an additional transition method by allowing entities to initially apply ASU 2016-02, and subsequent related standards, at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company adopted the new guidance on January 1, 2019 utilizing the transition method allowed per ASU 2018-11, and accordingly, comparative period financial information was not adjusted for the effects of the new guidance. No cumulative-effect adjustment was required to the opening balance of retained earnings on the adoption date. The Company's adoption of the new standard did not have any impact on the Company's condensed consolidated statements of operations or cash flows; however, the impact of adopting the new guidance resulted in a right-of-use asset and lease liability being recorded on the condensed consolidated balance sheet as of March 31, 2019 of approximately $400, which is included within other assets and accounts payable and other liabilities. In July 2018, the FASB issued ASU No. 2018-09, Codification Improvements. This update provides clarification, corrects errors in and makes minor improvements to various ASC topics. Many of the amendments in this update have transition guidance with effective dates for annual periods beginning after December 15, 2018 and some amendments in this update do not require transition guidance and were effective upon issuance of this update. The adoption of this standard did not have a material impact on the Company's condensed consolidated financial statements.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements: In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. This update introduces a current expected credit loss model for measuring expected credit losses for certain types of financial instruments held at the reporting date based on historical experience, current conditions and reasonable supportable forecasts. ASU 2016-13 replaces the current incurred loss model for measuring expected credit losses, requires expected losses on available-for-sale debt securities to be recognized through an allowance for credit losses rather than as reductions in the amortized cost of the securities, and provides for additional disclosure requirements. ASU 2016-13 is effective for interim and annual reporting periods beginning after December 15, 2019, with early adoption permitted for interim and annual reporting periods beginning after December 15, 2018. The Company is currently evaluating the effects the adoption of ASU 2016-13 will have on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, or ASU 2018-13. This update removes the disclosure requirements for the amounts of and the reasons for transfers between Level 1 and Level 2 and disclosure of the policy for timing of transfers between levels. This update also removes disclosure requirements for the valuation processes for Level 3 fair value measurements. Additionally, this update adds disclosure requirements for the changes in unrealized gains and losses for recurring Level 3 fair value measurements and quantitative information for certain unobservable inputs in Level 3 fair value measurements. ASU 2018-13 is effective for interim and annual reporting periods beginning after December 15, 2019. The Company is currently evaluating the effects the adoption of ASU 2018-13 will have on its consolidated financial statements.

Disclosure of accounting policy for investments in financial assets, including marketable securities (debt and equity securities with readily determinable fair values), investments accounted for under the equity method and cost method, securities borrowed and loaned, and repurchase and resale agreements. For marketable securities, the disclosure may include the entity's accounting treatment for transfers between investment categories and how the fair values for such securities are determined. Also, for all investments, an entity may describe its policy for assessing, recognizing and measuring impairment of the investment.