Fair Value Measurements (Details) - Recurring - USD ($)
$ in Thousands
Sep. 30, 2016
Dec. 31, 2015
Financial Assets    
Cash and cash equivalents $ 199,874 $ 143,180
Total financial assets 201,813 143,500
Financial Liabilities    
Warrant Liability   289
Total financial liabilities   289
Money market funds | Other current assets    
Financial Assets    
Restricted cash 320 320
Money market funds | Other non-current assets    
Financial Assets    
Restricted cash 1,619  
Level 1    
Financial Assets    
Cash and cash equivalents 199,874 143,180
Total financial assets 201,813 143,500
Level 1 | Money market funds | Other current assets    
Financial Assets    
Restricted cash 320 320
Level 1 | Money market funds | Other non-current assets    
Financial Assets    
Restricted cash $ 1,619  
Level 3    
Financial Liabilities    
Warrant Liability   289
Total financial liabilities   $ 289