Annual report pursuant to Section 13 and 15(d)

STOCK-BASED COMPENSATION (Fair value assumptions) (Details)

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STOCK-BASED COMPENSATION (Fair value assumptions) (Details)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Risk-free interest rate, minimum 2.68% 1.87% 1.24%
Risk-free interest rate, maximum 2.70% 2.27% 1.49%
Dividend yield 0.00% 0.00% 0.00%
Volatility factors, minimum 27.66% 25.88% 29.42%
Volatility factors, maximum 28.00% 27.58% 36.11%
Weighted average expected life (in years) 5 years 8 months 25 days 5 years 9 months 10 days 5 years 9 months 4 days