Borrowed Funds - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended		12 Months Ended
	Oct. 17, 2013	Aug. 04, 2005	Dec. 31, 2014	Dec. 31, 2007	Dec. 31, 2006	Dec. 31, 2013	Oct. 17, 2013	Aug. 04, 2005
Deposits [Line Items]
Prepaid of FHLB advances	$ 159.0						$ 159.0
Weighted average cost, FHLB advances	2.31%		1.18%			0.69%	2.31%
Weighted average term to maturity, FHLB advances	16 months
FHLB advances prepayment fee	4.3
Trust preferred securities issued				10.0	12.5
Trust preferred securities, principal maturity date				Sep. 01, 2037
Trust preferred securities, principal maturity date					2036
Subordinated debt issued		$ 5.0						$ 5.0
Subordinated debt at a fixed interest rate		6.35%
Maturity date of subordinated debt		Nov. 23, 2015
Minimum investment in the capital stock of the FHLB			0.20%
Specified value of certain transactions between the Bank and the FHLB			4.50%
Trust Preferred Securities [Member]
Deposits [Line Items]
Floating rate percentage				1.75%	1.66%
Floating rate description				3-month LIBOR	3-month LIBOR