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Fair Value Measurements - Activities of the marketable securities (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Fair value measurement [Abstract]        
Beginning balance     $ 1,287,500 $ 0
Purchases     6,479,147 6,039,567
Proceeds from sale     (3,328,157) (6,023,723)
Reclassification of net realized gains on marketable securities into earnings $ 22,428 $ 75,055 22,428 1,160,162
Unrealized (losses) gains on marketable securities (257,329) (38,527) (23,063) 28,995
Ending balance $ 4,437,855 $ 1,205,001 $ 4,437,855 $ 1,205,001