Reconciliation of shares used to determine net income per share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share Disclosure [Line Items]
Net income (loss)	$ 2,194	$ (113)	$ 9,837	$ 1,756
Weighted average number of shares - basic	23,928,081	23,780,606	23,834,685	23,780,606
Weighted average number of shares outstanding - diluted	26,566,674	23,780,606	26,241,273	24,921,835
Warrant
Earnings Per Share Disclosure [Line Items]
Shares underlying	398,492	0	297,826	14,856
Options
Earnings Per Share Disclosure [Line Items]
Shares underlying	2,240,101	0	2,108,762	1,126,373