Post-effective amendment to a registration statement that is not immediately effective upon filing

SIGNIFICANT RISKS AND UNCERTAINTIES (Details)

v3.21.1
SIGNIFICANT RISKS AND UNCERTAINTIES (Details) - Customer concentration
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Trade receivables    
Concentration risk    
Concentration risk (in percent)   10.00%
Revenue    
Concentration risk    
Concentration risk (in percent) 17.00% 18.00%