Condensed Financial Information of First Commonwealth Financial Corporation (Parent Company Only) - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2005	Dec. 31, 2004
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Cash Dividends Declared per Common Share (in dollars per share)	$ 0.23	$ 0.18	$ 0.12
Line of credit	$ 15,000,000				$ 14,000,000
Draw On Line Of Credit				8,500,000
Borrowings	$ 0	$ 0	$ 0