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CONVERTIBLE SENIOR NOTES - Additional Information (Details)
$ / shares in Units, shares in Millions
1 Months Ended 9 Months Ended
Jan. 31, 2018
USD ($)
day
Apr. 30, 2019
USD ($)
$ / shares
shares
Apr. 30, 2018
USD ($)
$ / shares
shares
Debt Instrument [Line Items]      
Number of securities called by warrants or rights (in shares) | shares     11.8
Payments for convertible note hedges   $ 0 $ 143,175,000
Exercise price of warrants (in dollars per share) | $ / shares     $ 73.46
Proceeds from issuance of warrants   0 $ 87,975,000
Transaction cost   $ (55,200,000)  
Dilutive effect of convertible securities (in shares) | shares   3.9  
Share price threshold for dilutive effect of convertible debt (in dollars per share) | $ / shares   $ 73.46  
Dilutive effect of $10 increase in share price (in shares) | shares   4.9  
Dilutive effect of warrants (in shares) | shares   1.4  
Share price threshold for dilutive effect of warrants (in dollars per share) | $ / shares   $ 83.46  
Common Class A      
Debt Instrument [Line Items]      
Share price (in dollars per share) | $ / shares   $ 43.19  
Convertible Debt      
Debt Instrument [Line Items]      
Interest rate, stated percentage     0.00%
Face amount     $ 575,000,000.0
Convertible debt     $ 75,000,000.0
Conversion ratio 20.4705    
Conversion price (in dollars per share) | $ / shares     $ 48.85
Threshold trading days | day 20    
Threshold consecutive trading days | day 30    
Threshold percentage of stock price trigger 130.00%    
Redemption price, percentage 100.00%    
Carrying amount of liability component     $ 423,400,000
Carrying amount of equity component     151,600,000
Unamortized discount and debt issuance costs, net     11,500,000
Unamortized discount, net     10,781,000
Debt issuance cost, gross, noncurrent     707,000
Transaction costs attributable to liability component     8,500,000
Transaction costs attributable to equity component   $ 3,000,000.0 $ 3,000,000.0
Debt instrument, term   44 months  
Payments for convertible note hedges $ 143,175,000    
Proceeds from issuance of warrants $ 87,975,000    
Convertible Debt | Common Class A      
Debt Instrument [Line Items]      
Threshold percentage of stock price trigger 98.00%