Fair Value Measurements (Details) (USD $)
12 Months Ended
Dec. 31, 2014
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Dec. 31, 2013
Assets    
Cash $ 28,518,000  
Liabilities    
Warrant liability   1,945,000
Number of work statements executed with the Nordic Work Statements 3  
Cash    
Assets    
Cash 1,519,000  
Money market    
Assets    
Cash 23,994,000  
Domestic corporate debt securities    
Assets    
Cash 3,005,000  
Recurring basis | Level 1    
Assets    
Cash 25,513,000  
Assets fair value   12,303,000
Recurring basis | Level 1 | Cash    
Assets    
Cash 1,519,000 2,710,000
Recurring basis | Level 1 | Money market    
Assets    
Money Market Funds 23,994,000 9,593,000
Recurring basis | Level 2    
Assets    
Cash 3,005,000  
Marketable securities 76,758,000  
Recurring basis | Level 2 | Domestic corporate debt securities    
Assets    
Marketable securities 69,509,000  
Recurring basis | Level 2 | Domestic corporate commercial paper    
Assets    
Money Market Funds 3,005,000  
Marketable securities 7,249,000  
Recurring basis | Level 3    
Liabilities    
Warrant liability   1,945,000
Stock liability   5,328,000
Total liabilities carried at fair value   7,273,000
Recurring basis | Estimated Fair Value    
Assets    
Cash 28,518,000  
Marketable securities 76,758,000  
Assets fair value   12,303,000
Liabilities    
Warrant liability   1,945,000
Stock liability   5,328,000
Total liabilities carried at fair value   7,273,000
Recurring basis | Estimated Fair Value | Cash    
Assets    
Cash 1,519,000 2,710,000
Recurring basis | Estimated Fair Value | Money market    
Assets    
Money Market Funds 23,994,000 9,593,000
Recurring basis | Estimated Fair Value | Domestic corporate debt securities    
Assets    
Marketable securities 69,509,000  
Recurring basis | Estimated Fair Value | Domestic corporate commercial paper    
Assets    
Money Market Funds 3,005,000  
Marketable securities $ 7,249,000