| **Subordinated Debentures**                       | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
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| **Disclosure Subordinated Debentures [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Subordinated Debentures                           | Subordinated DebenturesSubordinated Debentures outstanding at December 31 are as follows:   2013 2012 Due Amount Rate Amount Rate   (dollars in thousands)Owed to:         First Commonwealth Capital Trust I2029 $—   $33,583 9.50%First Commonwealth Capital Trust II2034 30,929 LIBOR + 2.85 30,929 LIBOR + 2.85First Commonwealth Capital Trust III2034 41,238 LIBOR + 2.85 41,238 LIBOR + 2.85Total  $72,167   $105,750  First Commonwealth has established three trusts, First Commonwealth Capital Trust I, First Commonwealth Capital Trust II, and First Commonwealth Capital Trust III, of which 100% of the common equity is owned by First Commonwealth. The trusts were formed for the purpose of issuing company obligated mandatorily redeemable capital securities to third-party investors and investing the proceeds from the sale of the capital securities solely in junior subordinated debt securities (“subordinated debentures”) of First Commonwealth. The subordinated debentures held by each trust are the sole assets of the trust.Interest on the debentures issued to First Commonwealth Capital Trust III is paid quarterly at a floating rate of LIBOR + 2.85% which is reset quarterly. Subject to regulatory approval, First Commonwealth may redeem the debentures, in whole or in part, at its option on any interest payment date at a redemption price equal to 100% of the principal amount of the debentures, plus accrued and unpaid interest to the date of the redemption. Deferred issuance costs of $630 thousand are being amortized on a straight-line basis over the term of the securities.Interest on the debentures issued to First Commonwealth Capital Trust II is paid quarterly at a floating rate of LIBOR + 2.85%, which is reset quarterly. Subject to regulatory approval, First Commonwealth may redeem the debentures, in whole or in part, at its option at a redemption price equal to 100% of the principal amount of the debentures, plus accrued and unpaid interest to the date of the redemption. Deferred issuance costs of $471 thousand are being amortized on a straight-line basis over the term of the securities.On January 29, 2013, the Company’s Board of Directors authorized the redemption of 100% of First Commonwealth Capital Trust I as of April 1, 2013, at a redemption price of 103.325% of the principal amount, plus accrued and unpaid interest. At the time of redemption,  a $1.1 million redemption premium was paid and $0.5 million in unamortized deferred issuance costs were recognized. Interest on debentures issued to First Commonwealth Capital Trust I was paid semiannually at a fixed rate of 9.50% and deferred issuance costs of $996 thousand were being amortized on a straight line basis over the term of the securities. |

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| - Definition
The entire disclosure for borrowings under subordinated debt agreements that qualify as available in computing net capital under SEC's uniform net capital rule, including restrictive covenants, collateral, interest rates and due dates, amounts due by date and amount owed in total.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-BRD -Paragraph 80 -Subparagraph Exhibit 4-8, 9 -IssueDate 2006-05-01 -Chapter 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-BRD -Paragraph 08 -IssueDate 2006-05-01 -Chapter 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.
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