Quarterly report pursuant to Section 13 or 15(d)

Common Stock - Additional Information (Detail)

v2.4.0.8
Common Stock - Additional Information (Detail) (USD $)
 1 Months Ended 6 Months Ended 84 Months Ended 6 Months Ended 1 Months Ended 6 Months Ended 1 Months Ended
May 31, 2013
Jun. 30, 2013
Plans
Jun. 30, 2012
Jun. 30, 2013
Plans
Sep. 30, 2012
Jun. 19, 2013
2013 Plan [Member]
Jun. 30, 2013
2013 ATM [Member]
Jun. 30, 2013
Market Issuance Sales Agreement [Member]
Oct. 31, 2012
2012 ATM [Member]
Jun. 30, 2013
2012 and 2013 ATMs [Member]
Jul. 31, 2013
Subsequent Event [Member]
Aug. 02, 2013
Subsequent Event [Member]
2013 ATM [Member]
Jul. 31, 2013
Subsequent Event [Member]
2013 ATM [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Common stock having an aggregate offering price         $ 75,000,000   $ 45,000,000       $ 200,000,000    
Public offering of Common Stock, amount                 30,000,000        
Maximum percentage of fee paid under agreement               3.00%          
Public offering of Common Stock, shares                   4,864,757   2,200,000  
Net proceeds from public offering of Common Stock   44,240,000 28,750,000 73,293,000           42,800,000   18,400,000  
Common stock having an aggregate offering price, additional amount                         70,000,000
Number of equity compensation plans   3   3                  
Common Stock to be issued as equity grants           2,300,000              
Stock-based compensation expense related to all unvested stock option   10,600,000   10,600,000                  
Stock-based compensation weighted-average vesting period   1 year 8 months 12 days                      
Stock issued during period shares employee stock purchase plans 21,505                        
Shares issued under employee stock purchase plan average price per share $ 3.88                        
Percentage of closing price for purchase price of common stock under employee stock purchase plan 85.00%                        
Closing price of common stock $ 4.56                        
Issuance of common stock   73,011                      
Issued warrants to purchase common stock   143,429                      
Warrant exercise price   5.18   5.18                  
Shares of common stock   340   340                  
Issuance of Warrant related to Hercules Note   $ 1,098