Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt - Novartis Note - Additional Information (Details)

v3.8.0.1
Long-Term Debt - Novartis Note - Additional Information (Details) - USD ($)
1 Months Ended
Sep. 22, 2017
Sep. 30, 2015
May 31, 2005
Mar. 31, 2018
Dec. 31, 2017
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%  
Outstanding principal balance       $ 14,600,000 $ 14,600,000
Novartis Note [Member] | Six-month LIBOR [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