Preferred Stock and Warrant - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended		12 Months Ended			9 Months Ended	0 Months Ended	1 Months Ended
	Sep. 29, 2010	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2013 Private Placement	Feb. 06, 2009 Series A Preferred Stock	Sep. 29, 2010 Capital Purchase Program (CPP)	Sep. 29, 2010 Capital Purchase Program (CPP) After Five Years	Sep. 29, 2010 Series CD Preferred Stock	Mar. 22, 2013 Series D Preferred Stock	Sep. 30, 2013 Convertible Preferred Stock
Class of Stock [Line Items]
Proceeds received from treasury								$ 5,000,000
Issuance of preferred stock, shares								5,000			12,123
Common Stock, shares repurchased								54,705
Warrant, exercise price								13.71
Warrant, term period								10 years
Preferred stock, annual dividend rate									5.00%	9.00%	2.00%
Capital purchase liquidation dividend term									5 years		8 years
Proceeds received from treasury, warrant								3,000,000
Net proceeds from issuance and redemption of preferred stock		18,958,000	0					4,700,000			12,123,000
Accretion of Series A Preferred Stock discount, maximum amount								5,000,000
Series UST Fixed rate cumulative perpetual preferred shares exchanged to Series CD Preferred stocks									5,000
Limitations on payment of dividends on common stock	no more than 100% of the aggregate per share dividend
Dividend declared and paid, common stock				$ 0.15	$ 0.15	$ 0.15
Preferred stock, no par value, $1,000 per share liquidation, 10,000,000 shares authorized; 17,123 issued and outstanding at June 30, 2013 and December 31, 2012, respectively		17,082,000		17,021,000								20,000,005
Preferred stock, issued		17,123		17,123								1,951,220
Preferred stock par value												$ 10.25
Common stock, shares, outstanding		5,107,131
Series CD fixed rate cumulative perpetual preferred shares issued in exchange to Series UST preferred stocks											5,000		1,951,220
Financial advisory fee							$ 921,487.43