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CREDIT RISK AND CONCENTRATION - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Concentration Risk    
Increase or decrease in interest rates of short-term investments that will not significantly affect the fair value of investment portfolio (as a percent) 10.00%  
Cash, Cash Equivalents and Short Term Investments | Countries Other than US | Credit Concentration Risk    
Concentration Risk    
Cash and cash equivalents and short-term investments $ 35.4 $ 51.0
Accounts Receivable | Customer Concentration Risk | Customer A    
Concentration Risk    
Concentration of risk (as a percent) 1.00% 1.00%
Accounts Receivable | Customer Concentration Risk | Customer B    
Concentration Risk    
Concentration of risk (as a percent) 91.00% 93.00%
Subsidiaries | Cash, Cash Equivalents and Short Term Investments | China | Credit Concentration Risk    
Concentration Risk    
Cash and cash equivalents and short-term investments $ 3.1 $ 8.9