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Fair Value Measurements - Fair value measurements of marketable securities (Details) - USD ($)
Sep. 30, 2021
Dec. 31, 2020
Sep. 30, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities $ 4,437,855 $ 1,287,500 $ 1,205,001 $ 0
Level 1        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities 4,437,855 1,287,500    
Level 2        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities 0 0    
Level 3        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities 0 0    
Equity securities        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities 4,437,855 1,287,500    
Equity securities | Level 1        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities 4,437,855 1,287,500    
Equity securities | Level 2        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities 0 0    
Equity securities | Level 3        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis        
Marketable securities $ 0 $ 0