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Condensed Financial Information of First Commonwealth Financial Corporation (Parent Company Only) - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2005 | Dec. 31, 2004
Lines Of Credit And Debt Obligations [Line Items] |  |  |  |  |
Cash Dividends Declared per Common Share | $ 0.18 | $ 0.12 | $ 0.06 |  |
Line of credit | $ 15,000,000 |  |  | $ 8,500,000 | $ 14,000,000
Borrowings | $ 0 | $ 0 | $ 0 |  |

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- Details
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- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770 + Details
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- Definition Amount borrowed under the credit facility as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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