Principal Accounting Policies - Disaggregation of Revenue (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Disaggregation of Revenue [Line Items] | |||
| Total revenues | $ 133,563,921 | $ 64,428,690 | $ 43,656,954 |
| PRC | |||
| Disaggregation of Revenue [Line Items] | |||
| Total revenues | 107,092,363 | 50,583,684 | 33,311,919 |
| United States | |||
| Disaggregation of Revenue [Line Items] | |||
| Total revenues | 10,019,248 | 5,296,269 | 4,582,105 |
| Others | |||
| Disaggregation of Revenue [Line Items] | |||
| Total revenues | $ 16,452,310 | $ 8,548,737 | $ 5,762,930 |