Annual report pursuant to Section 13 and 15(d)

Stock Plans and Stock-Based Compensation - Additional Information (Detail)

v2.4.0.8
Stock Plans and Stock-Based Compensation - Additional Information (Detail) (USD $)
 12 Months Ended 90 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
Nov. 29, 2013
Sep. 30, 2013
Dec. 19, 2011
Dec. 31, 2013
Employee Stock [Member]
May 31, 2013
Employee Stock [Member]
Nov. 30, 2012
Employee Stock [Member]
Dec. 02, 2013
Employee Stock [Member]
Nov. 29, 2013
Employee Stock [Member]
Dec. 03, 2012
Employee Stock [Member]
Dec. 31, 2013
Restricted Stock [Member]
Dec. 31, 2013
2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                            
Stock Based compensation, authorized number of shares                           2,300,000
Stock Based compensation, shares granted under the plan, net of cancellations 7,303,280                          
Stock Based compensation, shares available for issuance 996,720   996,720                     2,300,000
Stock Based compensation, Options Contractual term 10 years                          
Stock Based compensation, options, number of annual vesting                           7,303,280
Stock-based compensation expense related to all unvested stock option $ 3,400,000   $ 3,400,000                     $ 996,720,000,000
Stock-based compensation weighted-average vesting period 1 year 3 months 18 days                       5 years  
Employee Stock Purchase Plan to eligible employees, Authorized number of shares 200,000   200,000     200,000                
Employee Stock Purchase Plan to eligible employees, Reckoning fair value percentage during offering period 85.00%   85.00% 85.00%   85.00%     85.00%     85.00%    
Employee Stock Purchase Plan to eligible employees, Number of shares purchased by employees 49,214   49,214                      
Employee Stock Purchase Plan to eligible employees, Number of shares available for future sales 46,000 95,000 46,000                      
Employee Stock Purchase Plan to eligible employees, compensation expense recognized 46,000 95,000                        
Common Stock issued in connection with the first ESPP offering             6,065 21,505 21,644          
Share Based Compensation Restricted Stock Units 66,000   2,200,000                      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate                         114.20%  
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term                         5 years  
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate                         1.55%  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options                         7.6  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition 1 year 3 months 18 days                       5 years  
Common Stock Par Or Stated Value Per Share $ 0.001 $ 0.001 $ 0.001   $ 0.001     $ 3.88 $ 4.02 $ 1.39        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value $ 3.77                       $ 7,600,000  
Share Price                 $ 4.73   $ 1.64 $ 4.56