Subordinated Debentures (Additional Information) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Jul. 07, 2009	Aug. 10, 2004
Subordinated Borrowings [Abstract]
Trust Preferred Securities Issued			$ 35.0
Subordinated debt fixed interest rate		6.35%
Subordinated debt variable interest rate description	225 basis points over the three month Libor
Subordinated debt interest rate	2.48%
Subordinated debt maturity date	Oct. 07, 2034