Annual report pursuant to Section 13 and 15(d)

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

v3.8.0.1
STOCK-BASED COMPENSATION (Fair value assumptions) (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Risk-free interest rate, minimum 1.87% 1.24% 1.47%
Risk-free interest rate, maximum 2.27% 1.49% 1.75%
Dividend yield 0.00% 0.00% 0.00%
Volatility factors, minimum 25.88% 29.42% 34.18%
Volatility factors, maximum 27.58% 36.11% 43.36%
Weighted average expected life (in years) 5 years 9 months 10 days 5 years 9 months 4 days 5 years 11 months 8 days