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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) | 3 Months Ended
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Mar. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES |
Schedule of restricted cash and cash equivalents | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, | ​ | December 31, | ​
​ |  | 2021 |  | 2020 |
Cash and cash equivalents |  | $ | 123,191 |  | $ | 143,872 | ​
Restricted cash - current | ​ | ​ | 40,519 | ​ | ​ | 35,492 | ​
Restricted cash - noncurrent | ​ |  | 315 | ​ |  | 315 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash, cash equivalents and restricted cash |  | $ | 164,025 |  | $ | 179,679 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​

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- Definition Tabular disclosure of supplemental cash flow information for the periods presented. + References No definition available. + Details
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