Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Outstanding Debt Carrying Amount and Estimated Fair Value (Details)

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Fair Value Measurements - Outstanding Debt Carrying Amount and Estimated Fair Value (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Carrying Amount [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations $ 14,322 $ 43,167
Carrying Amount [Member] | Hercules Term Loan [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations   16,850
Carrying Amount [Member] | Novartis Note [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations 14,322 14,086
Carrying Amount [Member] | Servier Loan [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations   12,231
Estimated Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations 14,018 42,531
Estimated Fair Value [Member] | Hercules Term Loan [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations   16,453
Estimated Fair Value [Member] | Novartis Note [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations $ 14,018 13,836
Estimated Fair Value [Member] | Servier Loan [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest-bearing obligations   $ 12,242