Quarterly report pursuant to Section 13 or 15(d)

Net Loss Per Common Share - Calculation of Basic and Diluted Net Loss Per Share (Detail)

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Net Loss Per Common Share - Calculation of Basic and Diluted Net Loss Per Share (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 6 Months Ended 84 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Numerator:          
Net loss attributed to common stockholders $ (10,670) $ (6,455) $ (19,528) $ (13,011) $ (109,573)
Denominator:          
Weighted-average common shares outstanding-denominator for basic and diluted net loss per share 28,095,522 19,194,053 26,646,993 18,899,149  
Basic and diluted net loss per common share attributed to common stockholders $ (0.38) $ (0.34) $ (0.73) $ (0.69)