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Nature of Business (Details) - USD ($)
$ in Thousands
1 Months Ended 6 Months Ended 28 Months Ended
Jun. 30, 2020
Jun. 30, 2020
Jun. 30, 2020
May 31, 2020
Dec. 31, 2019
Liquidity          
Number of common stock issued 6,900,000        
Proceeds from offering of common stock, net of issuance costs $ 203,700 $ 203,964      
Accumulated deficit $ 610,517 $ 610,517 $ 610,517   $ 549,221
At Market Offering | Cowen and Company LLC ("Cowen")          
Liquidity          
Sales agreement amount of aggregate sale proceeds of common stock agreed to be issued       $ 150,000  
Overallotment Option          
Liquidity          
Number of common stock issued 900,000        
Public and Market Offering          
Liquidity          
Aggregate net proceeds     $ 648,700