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STOCK-BASED COMPENSATION - Weighted Average Grant Date Fair Value of Option Shares Granted and Assumptions Used (Details) - Stock options - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Stock Options      
Weighted average grant date fair value (in dollars per share) $ 10.67 $ 8.81 $ 12.34
Risk-free interest rate 1.53% 2.57% 2.72%
Dividend yield 1.14% 1.35% 1.02%
Volatility factor 24.00% 25.00% 29.00%
Expected option life 6 years 6 years 6 years