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Canadian Government Research and Development Program Liability - Narrative (Detail) - USD ($)
$ in Millions
 1 Months Ended
Apr. 30, 2019
Sep. 30, 2021
Dec. 31, 2020
Research and Development [Abstract]      
Lesser eligible costs percentage 22.14%    
Lesser eligible costs $ 23.0    
Funding repayment period 15 years    
Funding reduction percentage 50.00%    
Minimum costs of commercial plants $ 500.0    
Commercial plants constructed and operational period 30 months    
Funding liability   $ 6.5 $ 6.2