Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Stock Split	Stock Split The Board of Directors of ProAssurance Corporation (the Board) declared a two-for-one stock split effected December 27, 2012 in the form of a stock dividend. All share and per share information provided in this report reflects the effect of the split for all periods presented.
Accounting Changes Not Yet Adopted	Accounting Changes Not Yet Adopted Liabilities-Obligations Resulting from Joint and Several Liability Arrangements Effective for fiscal years beginning after December 15, 2013, the Financial Accounting Standards Board (FASB) revised guidance related to obligations resulting from joint and several liability arrangements. The new guidance requires an entity to recognize, measure and disclose obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date, except for obligations already addressed within existing GAAP guidance. The new guidance requires retrospective application to all prior periods presented for any such arrangements that exist at the beginning of the fiscal year of adoption. ProAssurance plans to adopt the guidance beginning January 1, 2014. Adoption of this guidance is not expected to have a material effect on ProAssurance's results of operations or financial position. Income Taxes-Presentation of Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists Effective for fiscal years beginning after December 15, 2013, the FASB issued guidance related to the financial statement presentation of unrecognized tax benefits. The new guidance requires an entity to present unrecognized tax benefits as a reduction to a deferred tax asset resulting from a net operating loss carryforward, a similar tax loss, or tax credit carryforward except in circumstances where relevant taxing authority does not permit offset or does not require offset and the entity does not intend to use the deferred tax asset for offset. The guidance requires prospective application for all unrecognized tax benefits that exist as of the effective date, but may be applied retrospectively. ProAssurance plans to adopt the guidance prospectively beginning January 1, 2014. Adoption of this guidance is expected to have no effect on ProAssurance's results of operations or financial position.
Accounting Changes Adopted	Accounting Changes Adopted Intangibles-Goodwill and Other Effective for fiscal years beginning after September 15, 2012, the FASB revised guidance related to impairment testing of indefinite-lived intangible assets. The new guidance permits an entity to assess qualitative factors to determine whether the existence of events and circumstances indicates that it is more likely than not that an indefinite-lived intangible asset is impaired. Quantitative impairment testing is required only if the assessment of qualitative factors indicates it is more likely than not that impairment exists. ProAssurance adopted the guidance on January 1, 2013. Adoption of this guidance had no material effect on ProAssurance's results of operations or financial position. Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income Effective for interim and annual reporting periods beginning after December 15, 2012, the FASB revised guidance related to the disclosure of amounts reclassified out of accumulated other comprehensive income. The most significant provisions of the new guidance require entities to present additional disclosure, either on the face of the income statement or in the notes, regarding significant amounts reclassified, in their entirety, from accumulated other comprehensive income to net income. ProAssurance adopted the guidance on January 1, 2013. Adoption of this guidance had no material effect on ProAssurance’s results of operations or financial position as it impacts disclosures only. Disclosures About Offsetting Assets and Liabilities Effective for fiscal years beginning on or after January 1, 2013, the FASB revised guidance related to disclosures about certain assets and liabilities in an entity’s financial statements. The guidance requires disclosures related to the net and gross positions of certain financial instruments and transactions that are either eligible for offset in accordance with existing GAAP guidance or subject to an agreement that requires such offset. The guidance must be applied retrospectively for all prior periods presented. ProAssurance adopted the guidance on January 1, 2013. Adoption of this guidance had no material effect on ProAssurance’s results of operations or financial position as it impacts disclosures only.

Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The Board of Directors of ProAssurance Corporation (the Board) declared a two-for-one stock split effected December 27, 2012 in the form of a stock dividend. All share and per share information provided in this report reflects the effect of the split for all periods presented.

Accounting Changes Not Yet Adopted

Liabilities-Obligations Resulting from Joint and Several Liability Arrangements

Effective for fiscal years beginning after December 15, 2013, the Financial Accounting Standards Board (FASB) revised guidance related to obligations resulting from joint and several liability arrangements. The new guidance requires an entity to recognize, measure and disclose obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date, except for obligations already addressed within existing GAAP guidance. The new guidance requires retrospective application to all prior periods presented for any such arrangements that exist at the beginning of the fiscal year of adoption. ProAssurance plans to adopt the guidance beginning January 1, 2014. Adoption of this guidance is not expected to have a material effect on ProAssurance's results of operations or financial position.

Income Taxes-Presentation of Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists

Effective for fiscal years beginning after December 15, 2013, the FASB issued guidance related to the financial statement presentation of unrecognized tax benefits. The new guidance requires an entity to present unrecognized tax benefits as a reduction to a deferred tax asset resulting from a net operating loss carryforward, a similar tax loss, or tax credit carryforward except in circumstances where relevant taxing authority does not permit offset or does not require offset and the entity does not intend to use the deferred tax asset for offset. The guidance requires prospective application for all unrecognized tax benefits that exist as of the effective date, but may be applied retrospectively. ProAssurance plans to adopt the guidance prospectively beginning January 1, 2014. Adoption of this guidance is expected to have no effect on ProAssurance's results of operations or financial position.

Accounting Changes Adopted

Intangibles-Goodwill and Other

Effective for fiscal years beginning after September 15, 2012, the FASB revised guidance related to impairment testing of indefinite-lived intangible assets. The new guidance permits an entity to assess qualitative factors to determine whether the existence of events and circumstances indicates that it is more likely than not that an indefinite-lived intangible asset is impaired. Quantitative impairment testing is required only if the assessment of qualitative factors indicates it is more likely than not that impairment exists. ProAssurance adopted the guidance on January 1, 2013. Adoption of this guidance had no material effect on ProAssurance's results of operations or financial position.

Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income

Effective for interim and annual reporting periods beginning after December 15, 2012, the FASB revised guidance related to the disclosure of amounts reclassified out of accumulated other comprehensive income. The most significant provisions of the new guidance require entities to present additional disclosure, either on the face of the income statement or in the notes, regarding significant amounts reclassified, in their entirety, from accumulated other comprehensive income to net income. ProAssurance adopted the guidance on January 1, 2013. Adoption of this guidance had no material effect on ProAssurance’s results of operations or financial position as it impacts disclosures only.

Disclosures About Offsetting Assets and Liabilities

Effective for fiscal years beginning on or after January 1, 2013, the FASB revised guidance related to disclosures about certain assets and liabilities in an entity’s financial statements. The guidance requires disclosures related to the net and gross positions of certain financial instruments and transactions that are either eligible for offset in accordance with existing GAAP guidance or subject to an agreement that requires such offset. The guidance must be applied retrospectively for all prior periods presented. ProAssurance adopted the guidance on January 1, 2013. Adoption of this guidance had no material effect on ProAssurance’s results of operations or financial position as it impacts disclosures only.