Loans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended							1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013 Performing [Member] SecurityLoan	Dec. 31, 2012 Performing [Member]	Sep. 30, 2013 Real estate - ITIN loans [Member]	Dec. 31, 2012 Real estate - ITIN loans [Member]	Sep. 30, 2013 Commitments to extend credit [Member]	Sep. 30, 2013 Commercial real estate [Member]	Dec. 31, 2012 Commercial real estate [Member]	Oct. 31, 2013 Commercial real estate [Member] Subsequent Event [Member]
Noncancelable Obligations Future Minimum Payments Due [Line Items]
Amount of net premium included in gross loans	$ 44,000		$ 44,000		$ 24,000
Period of loan past due			90 days
Frequency of external appraisals updating			Six to twelve months
Age of appraisals that will considered as stale			1 year
Impaired loans received														2,100,000
Recovered previously charged off impaired loans														1,300,000
Interest recovered	112,000	137,000	334,000	297,000										53,000
Additional interest income , net of tax	309,000	167,000	806,000	409,000
Impaired loans	45,462,000		45,462,000		47,660,000		5,400,000	8,600,000				20,053,000	29,077,000
Percentage of collateral coverage to loan balance			100.00%
Obligations to lend additional funds on restructured loans	0		0		0
Troubled debt restructurings	26,500,000		26,500,000		24,700,000
Performing according to their restructured terms			111				111
TDRs percentage of gross portfolio loans	4.53%		4.53%		3.71%
Doubtful grade remaining outstanding period			6 months
Allowance for credit losses, Ending balance	13,542,000		13,542,000		11,103,000	10,622,000
Percentage of allowance for loan and lease losses	2.28%		2.28%		1.67%
Impaired loans, Related Allowance	4,348,000		4,348,000		2,301,000				1,100	1,500		275,000	194,000
Allowance allocation ITIN portfolio commitments to extend credit											187,500,000
Reserve for off balance sheet commitments	698,000		698,000
Company reclassified mortgage loans held-for-sale					65,100,000
Decrease in secured commercial loan balance			$ 65,100,000
Loans and Leases Receivable, Other Information			Approximately 71% of our gross loan portfolio is secured by real estate, and a significant decline in real estate market values may require an increase in the ALLL
Percentage of loan portfolio is secured by real estate	0.00%		0.00%
Percentage of unallocated allowance amount out of ALLL			15.00%		7.00%
Maximum loan-to-value percentage			80.00%