Trust Preferred Securities - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended			12 Months Ended		1 Months Ended		12 Months Ended
	Aug. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 31, 2010 Common Stock [Member]	Aug. 31, 2010 Trust I [Member]	May 31, 2007 Trust I [Member]	Dec. 31, 2012 Trust I [Member]	Dec. 31, 2011 Trust I [Member]	Aug. 31, 2010 Trust II [Member]	May 31, 2007 Trust II [Member]	Dec. 31, 2012 Trust II [Member]	Dec. 31, 2011 Trust II [Member]
Trust Preferred Securities [Line Items]
Preferred securities sold to outside investors							$ 10,000,000
Floating interest rate period							three-month LIBOR				three-month LIBOR
LIBOR basis points							1.48%				1.48%
Fixed interest rate of Trust II											6.64%
Effective interest rate								1.79%				6.64%
Accrued interest payable		882,000	1,118,000					5,000	7,000			21,000	0
Maturity date of subordinate notes		Jun. 15, 2037
Amount of principal securities exchanged for common stock						2,125				2,125
Shares issued from conversion of preferred securities					462,234
Weighted average price of shares issued from securities conversion (in usd per share)	$ 4.41
Net gain on extinguishment of debt	2,210	0	0	2,210,000
Balance of the subordinated notes payable		$ 16,238,000	$ 16,238,000					$ 8,119,000				$ 8,119,000