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INCOME TAXES - Additional Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Taxes [Line Items]        
One-time charge due to enactment of the Tax Cuts and Jobs Act (TCJA) $ 11,500      
Effective income tax rate without TCJA   22.80%    
Income tax expense without TCJA   $ 34,200    
Current income tax expense   $ 15,406 $ 12,902 $ 10,224
Withholding tax rate for royalty payments   16.50%    
State and foreign income tax returns subject to examination period minimum (in years)   3 years    
State and foreign income tax returns subject to examination period maximum (in years)   4 years    
South Korea [Member]        
Income Taxes [Line Items]        
Current income tax expense   $ 14,900 $ 12,400 $ 9,900
ASU No. 2016-09 [Member]        
Income Taxes [Line Items]        
Cumulative effect adjustment on retained earnings resulting from adoption of accounting standard   $ 26,500