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STOCK-BASED COMPENSATION - Summary of Assumptions Used in Total Stockholder Return-Based Stock Units Valuation (Details) - TSR Units
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Assumptions used in fair value valuation      
Expected dividend yield (assuming full reinvestment) 0.00% 0.00% 0.00%
Minimum      
Assumptions used in fair value valuation      
Risk free interest rate 1.57% 2.36% 1.42%
Expected stock price volatility 23.80% 28.57% 28.86%
Expected service period 2 years 4 months 24 days 2 years 6 months 2 years 2 months 12 days
Maximum      
Assumptions used in fair value valuation      
Risk free interest rate 2.54% 2.59% 1.99%
Expected stock price volatility 28.57% 30.02% 30.97%
Expected service period 3 years 3 years 3 years