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Summary of Significant Accounting Policies - Summary of changes in fair value (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2020
Sep. 26, 2020
Jun. 27, 2020
Mar. 28, 2020
Dec. 31, 2019
Sep. 28, 2019
Jun. 29, 2019
Mar. 30, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                      
Beginning balance       $ 0       $ 1,918 $ 0 $ 1,918  
Fair value of warrants issued during the period                   0  
Change in fair value of warrant liability $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 11,744 $ 759 $ 0 12,503 $ 1,120
Reclassification of warrant liability to additional paid-in capital in connection with the IPO                   (14,421)  
Ending balance         $ 0         $ 0 $ 1,918