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BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Risks and Uncertainties) (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Concentration Risk [Line Items]        
Total cash $ 937,688 $ 771,711 $ 582,855 $ 364,664
Belarus, Russia, Ukraine, Kazakhstan, Armenia and Uzbekistan | Geographic Concentration Risk | Total Cash        
Concentration Risk [Line Items]        
Total cash 206,485      
Belarus | Geographic Concentration Risk | Total Cash        
Concentration Risk [Line Items]        
Total cash $ 123,370