Annual report pursuant to Section 13 and 15(d)

Summary of Business and Significant Accounting Principles - Warranty Accrual (Details)

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Summary of Business and Significant Accounting Principles - Warranty Accrual (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Movement in Standard Product Warranty Accrual [Roll Forward]    
Balance, beginning of year $ 6,001,864 $ 7,058,769
Accrual for warranty (1) 2,115,762 92,191
Warranty costs incurred (2,717,626) (1,149,096)
Balance, end of year $ 5,400,000 $ 6,001,864