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Income Taxes - Additional Information (Detail) (USD $)
 1 Months Ended 12 Months Ended
Aug. 31, 2004
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Income Taxes [Line Items]        
Change in the valuation allowance   $ 66,800,000 $ 60,700,000 $ 57,200,000
Federal operating loss carryforwards   1,700,000,000    
State operating loss carryforwards   1,200,000,000    
Net operating loss carryforwards 216,000,000      
Net operating loss and credit carryforwards, annual use limitation 13,000,000      
Federal
        
Income Taxes [Line Items]        
Net operating loss carry-forwards, expiration year   2018    
Research and development credits subject to expiration   45,000,000    
Federal research and development credits begin to expire   2024    
State
        
Income Taxes [Line Items]        
Net operating loss carry-forwards, expiration year   2014    
Research and development credits not subject to expiration   $ 38,000,000