Reconciliation of shares used to determine net income per share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share Disclosure [Line Items]
Net income	$ 5,135	$ 781	$ 7,644	$ 1,869
Weighted average number of shares - basic	23,841,996	23,780,606	23,813,776	23,780,606
Weighted average number of shares outstanding - diluted	26,177,960	24,989,119	26,149,740	25,082,275
Warrant
Earnings Per Share Disclosure [Line Items]
Shares underlying	277,867	16,746	277,867	22,455
Options
Earnings Per Share Disclosure [Line Items]
Shares underlying	2,058,097	1,191,767	2,058,097	1,279,214