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EQUITY-BASED COMPENSATION - Performance-Based Restricted Stock Activity (Details) - Performance Shares - Equity Plan - $ / shares
1 Months Ended 12 Months Ended
Mar. 31, 2019
Feb. 28, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Fair Value Assumptions          
Grant-date fair value (in dollars per share)     $ 131.30    
Performance Restricted Stock Units          
Unvested, beginning balance (in shares)     196,203    
Granted (in shares)   117,423 356,227    
Vested (in shares)     (176,976)    
Forfeited (in shares)     (103,635)    
Unvested, ending balance (in shares)     271,819 196,203  
Weighted Average Grant-Date Fair Value          
Unvested, beginning balance (in dollars per share)     $ 169.76    
Granted (in dollars per share)     131.30    
Vested (in dollars per share)     93.32    
Forfeited (in dollars per share)     155.23    
Unvested, ending balance (in dollars per share)     $ 147.07 $ 169.76  
Maximum units could be awarded (in shares)     543,638    
Two-Year          
Fair Value Assumptions          
Grant-date fair value (in dollars per share)         $ 162.13
Risk-free rate         1.27%
Company volatility         39.32%
Performance Restricted Stock Units          
Granted (in shares) 199,723        
Weighted Average Grant-Date Fair Value          
Granted (in dollars per share)         $ 162.13
Three-Year          
Fair Value Assumptions          
Grant-date fair value (in dollars per share)     $ 137.22 $ 170.45 $ 168.73
Risk-free rate     2.55% 1.99% 1.59%
Company volatility     35.00% 35.90% 41.14%
Performance Restricted Stock Units          
Granted (in shares) 32,958        
Weighted Average Grant-Date Fair Value          
Granted (in dollars per share)     $ 137.22 $ 170.45 $ 168.73
Five-Year          
Fair Value Assumptions          
Grant-date fair value (in dollars per share)     132.48    
Weighted Average Grant-Date Fair Value          
Granted (in dollars per share)     $ 132.48