Annual report pursuant to Section 13 and 15(d)

Property and Equipment - Additional Information (Detail)

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Property and Equipment - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Property, Plant and Equipment [Line Items]      
Depreciation and amortization $ 200,000 $ 200,000 $ 300,000
Property and equipment, historical asset values 2,552,000 2,293,000  
South San Francisco facility [Member]
      
Property, Plant and Equipment [Line Items]      
Leasehold improvements   500,000  
Leasehold improvements [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment, historical asset values 523,000 640,000  
Leasehold improvements [Member] | Redwood City, California [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment, historical asset values   2,700,000  
Computer and office equipment [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment, historical asset values 436,000 337,000  
Computer and office equipment [Member] | Redwood City, California [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment, historical asset values   $ 600,000