Reconciliation of shares used to determine net income per share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share Disclosure [Line Items]
Net income	$ 12,801	$ 1,034
Weighted average number of shares - basic	23,906,706	23,780,814
Weighted average number of shares outstanding - diluted	26,353,960	24,803,047
Warrants
Earnings Per Share Disclosure [Line Items]
Shares underlying	315,494	10,966
Options
Earnings Per Share Disclosure [Line Items]
Shares underlying	2,131,760	1,011,267