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SHARE-BASED COMPENSATION - Additional Information (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares reserved for future issuance 2.6  
Options exercisable, number of shares 4.8  
Options exercisable, weighted-average exercise price (usd per share) $ 174.13  
Restricted Stock Units (RSUs)    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares reserved for future issuance 1.1  
ESPP    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Employee Stock Purchase Plan, number of shares purchased by employees 0.1 0.1
Employee Stock Purchase Plan, value of shares purchased by employees $ 30.3 $ 25.3