Annual report pursuant to Section 13 and 15(d)

Long-Term Debt and Other Financings - Novartis Note - Additional Information (Details)

v3.8.0.1
Long-Term Debt and Other Financings - Novartis Note - Additional Information (Details) - USD ($)
 1 Months Ended 12 Months Ended
Sep. 22, 2017
Sep. 30, 2015
May 31, 2005
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2007
Novartis Note [Member]              
Debt Instrument [Line Items]              
Maturity date     Jun. 30, 2015        
Research and development expenses funded through loan facility, maximum     75.00%        
Maximum borrowing capacity under loan agreement     $ 50,000,000        
Interest rate at period end       3.81%      
Accrued interest payable       $ 300,000 $ 400,000 $ 300,000  
Outstanding principal balance       $ 14,600,000 $ 14,100,000    
Novartis Note [Member] | Six-month London Interbank Offered Rate [Member]              
Debt Instrument [Line Items]              
Basis spread on variable rate             2.00%
Secured Note Amendment [Member]              
Debt Instrument [Line Items]              
Maturity date Sep. 30, 2022 Sep. 30, 2020          
Reduction in outstanding principal amount   $ 7,300,000