Subordinated Debentures - Additional Information (Detail) (USD $)		12 Months Ended		0 Months Ended	12 Months Ended
	Dec. 31, 2013 First Commonwealth Capital Trust [Member]	Dec. 31, 2013 First Commonwealth Capital Trust III [Member]	Dec. 31, 2013 First Commonwealth Capital Trust II [Member]	Apr. 02, 2013 First Commonwealth Capital Trust I [Member]	Dec. 31, 2012 First Commonwealth Capital Trust I [Member]	Dec. 31, 2013 First Commonwealth Capital Trust I [Member]	Dec. 31, 2013 LIBOR [Member] Subordinated Debt [Member] First Commonwealth Capital Trust III [Member]	Dec. 31, 2012 LIBOR [Member] Subordinated Debt [Member] First Commonwealth Capital Trust III [Member]	Dec. 31, 2013 LIBOR [Member] Subordinated Debt [Member] First Commonwealth Capital Trust II [Member]	Dec. 31, 2012 LIBOR [Member] Subordinated Debt [Member] First Commonwealth Capital Trust II [Member]
Subordinated Borrowing [Line Items]
Percentage of common equity owned by First Commonwealth	100.00%
Variable interest rate							2.85%	2.85%	2.85%	2.85%
Deferred issuance costs				$ 500,000
Debentures authorized for redemption percentage				100.00%
Redemption price as percentage of principal amount		100.00%	100.00%	103.325%
Deferred finance costs		630,000	471,000			996,000
Redemption Premium				$ 1,100,000
Fixed interest rate				9.50%	9.50%