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Research Funding (Details) - USD ($)
$ in Thousands
 1 Months Ended 12 Months Ended 44 Months Ended
Sep. 30, 2020
May 31, 2019
Mar. 31, 2018
Dec. 31, 2017
May 31, 2017
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2020
Feb. 28, 2017
Research and Development [Abstract]                  
Grants awarded           $ 8,600   $ 8,600 $ 12,200
Funding of grant award         $ 5,700     $ 8,200  
Milestone payment received on grant award       $ 1,900          
Progress payment received on grant award     $ 300            
Progress payment amortized to related research and development over estimated award period $ 46 $ 200              
Amortization of accrued grant funding to offset expense           $ 1,600 $ 2,700