Borrowings - Junior Subordinated Debt Trusts (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 58,285	$ 58,246
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	57,500
Common Stock Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	1,779
F.N.B. Statutory Trust II [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22,165
Stated Maturity Date	Jun. 15, 2036
Interest Rate	1.99%
Description of variable rate	Variable; 3-month LIBOR + 165 basis points (bps)
Basis points	1.65%
F.N.B. Statutory Trust II [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 21,500
F.N.B. Statutory Trust II [Member] | Common Stock Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	665
Omega Financial Capital Trust I [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 36,120
Stated Maturity Date	Oct. 18, 2034
Interest Rate	2.48%
Description of variable rate	Variable; 3-month LIBOR + 219 bps
Basis points	2.19%
Omega Financial Capital Trust I [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 36,000
Omega Financial Capital Trust I [Member] | Common Stock Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 1,114