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Summary of Significant Accounting Policies - Patent Costs (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Accounting Policies [Abstract]        
Patent costs $ 0.3 $ 0.4 $ 1.4 $ 1.6