Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended				1 Months Ended			1 Months Ended			1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Unvested Restricted Common Stock	Jul. 16, 2012 Vested options held by 3 employees	Jul. 16, 2012 Vested options held by 3 employees Minimum	Jul. 16, 2012 Vested options held by 3 employees Maximum	Jul. 16, 2012 Unvested options held by 2 employees	Jul. 16, 2012 Unvested options held by 2 employees Minimum	Jul. 16, 2012 Unvested options held by 2 employees Maximum	May 31, 2013 Vested options held by 1 employees	May 31, 2013 Vested options held by 1 employees Minimum	May 31, 2013 Vested options held by 1 employees Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, granted	1,315,500	361,900	1,426,400	425,400
Weighted-average grant date fair value	$ 1.77	$ 3.51	$ 1.89	$ 3.48
Unrecognized compensation costs	$ 6.3		$ 6.3
Expected recognition period			1 year 8 months 27 days		1 year 5 months 9 days
Share Based Compensation Arrangement By Share Based Payment Award Option Fully Vested						829,488						66,667
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period							12 months	18 months		6 months	12 months		3 months	12 months
Share Based Compensation Arrangement By Share Based Payment Award Unvested Options									200,000
Share Based Compensation Arrangement By Share Based Payment Award Unvested Shares Of Restricted Stocks									147,427
Unrecognized compensation costs					$ 1.4