New Accounting Pronouncements (Notes)	9 Months Ended
Sep. 30, 2018
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)," in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. Additionally, the FASB issued ASU No. 2018-01, "Leases (Topic 842)" in January 2018 and ASU No. 2018-11, "Leases - Targeted Improvements" in July 2018. Both of these ASU's provide certain improvements and optional practical expedients to Topic 842. Under this new guidance, all entities will classify leases to determine how to recognize lease-related revenue and expense. Quantitative and qualitative disclosures will be required by lessees and lessors to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The intention is to require enough information to supplement the amounts recorded in the financial statements so that users can understand more about the nature of an entity’s leasing activities. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. First Commonwealth has elected the transition option provided in ASU No. 2018-11, which provides for the modified retrospective approach to be applied on January 1, 2019. We have established a lease implementation team, which includes members of finance, facilities, information technology and operations. The implementation team has analyzed data on leased assets, assessed the impact of the new standard on disclosures, processes and internal controls over financial reporting and evaluated the election of certain practical expedients. During the third quarter of 2018, the implementation of a third-party software was completed in order to assist with evaluating the impact of this ASU. The implementation team continues to validate data input into the third-party software as well as finalize disclosures and internal controls. This new standard will increase assets and liabilities for the right-of-use assets and associated lease liabilities but is not expected to have a material impact on First Commonwealth's financial condition or results of operations. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,” which amends the guidance for recognizing credit losses from an “incurred loss” methodology that delays recognition of credit losses until it is probable a loss has been incurred to an expected credit loss methodology. The Current Expected Credit Loss ("CECL") methodology requires the use of the modified retrospective transition method by means of a cumulative-effect adjustment to equity as of the beginning of the period in which the guidance is adopted. The standard is effective for the Company as of January 1, 2020. We have established a CECL implementation team, which includes members from the finance and credit areas, with oversight by the Chief Executive Officer, Chief Financial Officer and Chief Credit Officer. During the third quarter, Management completed the implementation of a third party software to assist with this ASU. Management is currently evaluating the impact of the amended guidance on First Commonwealth’s financial condition or results of operations. In January 2017, the FASB issued ASU No. 2017-04, "Intangibles-Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment" which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under this ASU, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. Impairment should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to the reporting unit. Income tax effects from any tax deductible goodwill should be taken into consideration of the carrying amount of the reporting unit when measuring for goodwill impairment, if applicable. An entity still has the option to perform the qualitative assessment for the reporting unit to determine if the quantitative impairment test is necessary. This standard is effective for interim and annual periods for fiscal years beginning after December 15, 2019. The adoption of this ASU is not expected to have a material impact on First Commonwealth’s financial condition or results of operations. In August 2017, the FASB issued ASU No. 2017-12, "Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities" with the objective of improving the financial reporting of hedging relationships to better portray the economic results of risk management activities in its financial statements. The main provisions of this ASU update the hedge accounting model to expand the ability to hedge risk, reduce complexity, and ease certain documentation and assessment requirements. It also eliminates the requirement to separately measure and report hedge ineffectiveness, and generally requires the change in fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The standard is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The adoption of this ASU is not expected to have a material impact on First Commonwealth’s financial condition or results of operations. In February 2018, the FASB issued ASU No. 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 22)" allowing a reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act. This amendment also requires certain disclosures about the stranded tax effects, including disclosure of the policy for releasing income tax effects from accumulated other comprehensive income and the impact if the entity elected to reclassify the income tax effects or, if the entity did not elect to reclassify, a statement that the entity did not elect to reclassify. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company adopted this ASU as of January 1, 2018. Adoption of this ASU did not have a material impact on First Commonwealth's financial condition or results of operations. In August 2018, the FASB issued ASU No. 2018-13, "Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement." This ASU updates disclosure requirements for fair value measurements, including elimination of the disclosure related to the amount and reason for transfers between Level 1 and Level 2 of the fair value hierarchy. ASU No. 2018-13 is effective for interim and annual reporting periods beginning after December 15, 2019. Adoption of this ASU will not have a material impact on First Commonwealth's financial condition or results of operations, as it relates only to disclosure requirements.

New Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)," in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. Additionally, the FASB issued ASU No. 2018-01, "Leases (Topic 842)" in January 2018 and ASU No. 2018-11, "Leases - Targeted Improvements" in July 2018. Both of these ASU's provide certain improvements and optional practical expedients to Topic 842. Under this new guidance, all entities will classify leases to determine how to recognize lease-related revenue and expense. Quantitative and qualitative disclosures will be required by lessees and lessors to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The intention is to require enough information to supplement the amounts recorded in the financial statements so that users can understand more about the nature of an entity’s leasing activities. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. First Commonwealth has elected the transition option provided in ASU No. 2018-11, which provides for the modified retrospective approach to be applied on January 1, 2019. We have established a lease implementation team, which includes members of finance, facilities, information technology and operations. The implementation team has analyzed data on leased assets, assessed the impact of the new standard on disclosures, processes and internal controls over financial reporting and evaluated the election of certain practical expedients. During the third quarter of 2018, the implementation of a third-party software was completed in order to assist with evaluating the impact of this ASU. The implementation team continues to validate data input into the third-party software as well as finalize disclosures and internal controls. This new standard will increase assets and liabilities for the right-of-use assets and associated lease liabilities but is not expected to have a material impact on First Commonwealth's financial condition or results of operations.

In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,” which amends the guidance for recognizing credit losses from an “incurred loss” methodology that delays recognition of credit losses until it is probable a loss has been incurred to an expected credit loss methodology. The Current Expected Credit Loss ("CECL") methodology requires the use of the modified retrospective transition method by means of a cumulative-effect adjustment to equity as of the beginning of the period in which the guidance is adopted. The standard is effective for the Company as of January 1, 2020. We have established a CECL implementation team, which includes members from the finance and credit areas, with oversight by the Chief Executive Officer, Chief Financial Officer and Chief Credit Officer. During the third quarter, Management completed the implementation of a third party software to assist with this ASU. Management is currently evaluating the impact of the amended guidance on First Commonwealth’s financial condition or results of operations.

In January 2017, the FASB issued ASU No. 2017-04, "Intangibles-Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment" which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under this ASU, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. Impairment should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to the reporting unit. Income tax effects from any tax deductible goodwill should be taken into consideration of the carrying amount of the reporting unit when measuring for goodwill impairment, if applicable. An entity still has the option to perform the qualitative assessment for the reporting unit to determine if the quantitative impairment test is necessary. This standard is effective for interim and annual periods for fiscal years beginning after December 15, 2019. The adoption of this ASU is not expected to have a material impact on First Commonwealth’s financial condition or results of operations.

In August 2017, the FASB issued ASU No. 2017-12, "Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities" with the objective of improving the financial reporting of hedging relationships to better portray the economic results of risk management activities in its financial statements. The main provisions of this ASU update the hedge accounting model to expand the ability to hedge risk, reduce complexity, and ease certain documentation and assessment requirements. It also eliminates the requirement to separately measure and report hedge ineffectiveness, and generally requires the change in fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The standard is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The adoption of this ASU is not expected to have a material impact on First Commonwealth’s financial condition or results of operations.

In February 2018, the FASB issued ASU No. 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 22)" allowing a reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act. This amendment also requires certain disclosures about the stranded tax effects, including disclosure of the policy for releasing income tax effects from accumulated other comprehensive income and the impact if the entity elected to reclassify the income tax effects or, if the entity did not elect to reclassify, a statement that the entity did not elect to reclassify. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company adopted this ASU as of January 1, 2018. Adoption of this ASU did not have a material impact on First Commonwealth's financial condition or results of operations.

In August 2018, the FASB issued ASU No. 2018-13, "Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement." This ASU updates disclosure requirements for fair value measurements, including elimination of the disclosure related to the amount and reason for transfers between Level 1 and Level 2 of the fair value hierarchy. ASU No. 2018-13 is effective for interim and annual reporting periods beginning after December 15, 2019. Adoption of this ASU will not have a material impact on First Commonwealth's financial condition or results of operations, as it relates only to disclosure requirements.