Long-Term Obligation (Narrative) (Details) - USD ($)
1 Months Ended 12 Months Ended 41 Months Ended
Feb. 29, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2015
Dec. 31, 2012
Aug. 31, 2012
Debt Instrument [Line Items]              
Aggregate payments to long-term obligations   $ 9,207,000 $ 4,856,000 $ 1,025,000      
Accretion of interest expense   2,848,000 3,678,000 4,410,000      
Cash and cash equivalents   40,435,000 24,248,000 $ 54,877,000 $ 40,435,000 $ 93,032,000  
Financing Agreement with Biopharma              
Debt Instrument [Line Items]              
Cumulative payments to be made under financing agreement   45,000,000     $ 45,000,000   $ 45,000,000
Aggregate payments to long-term obligations   $ 15,100,000          
Payment obligation based on a percentage of net product sales   20.00%          
Percentage of payments received for upfront, milestone or other contingent fees   20.00%     20.00%    
Interest expense on long-term obligation   $ 2,800,000 3,700,000        
Accretion of interest expense         $ 12,600,000    
Long term debt obligation   27,500,000 $ 33,900,000   27,500,000   30,000,000
Issuance costs capitalized   140,000     140,000    
Unamortized issuance cost   35,000     35,000    
Financing Agreement with Biopharma | Subsequent Events              
Debt Instrument [Line Items]              
Aggregate payments to long-term obligations $ 3,000,000            
Minimum | Financing Agreement with Biopharma | Cash Required Under Debt Covenants              
Debt Instrument [Line Items]              
Cash and cash equivalents   50,000,000     50,000,000    
Maximum | Financing Agreement with Biopharma              
Debt Instrument [Line Items]              
Cumulative payments to be made under financing agreement   $ 45,000,000     $ 45,000,000   $ 45,000,000
Payment obligation based on a percentage of net product sales   50.00%