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INCENTIVE STOCK PLANS - Schedule of Assumptions used for Performance Shares (Details) - Performance Shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 32.60% 18.40% 20.80%
Risk-free rate 0.30% 2.30% 2.40%