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Convertible Senior Notes (Details)
1 Months Ended 12 Months Ended
Mar. 31, 2018
USD ($)
day
shares
Jul. 31, 2020
USD ($)
$ / shares
Jul. 31, 2019
USD ($)
Jul. 31, 2018
USD ($)
Debt Instrument [Line Items]        
Principal   $ 400,000,000 $ 400,000,000  
Proceeds from issuance of convertible senior notes, net of issuance costs $ 387,200,000 $ 0 $ 0 $ 387,239,000
Convertible conversion price (in dollars per share) | $ / shares   $ 113.75    
Senior Notes | Convertible Debt        
Debt Instrument [Line Items]        
Principal $ 400,000,000.0      
Stated interest rate 1.25%      
Proceeds from issuance of convertible senior notes, net of issuance costs   $ 387,200,000    
Senior Notes | Convertible Debt | On or after October 15, 2024        
Debt Instrument [Line Items]        
Number of shares issuable, per 1,000 principal converted (in shares) | shares 8.7912      
Convertible conversion price (in dollars per share) | $ / shares   $ 113.75    
Senior Notes | Convertible Debt | On or after March 20, 2022        
Debt Instrument [Line Items]        
Debt instrument, redemption. percentage 100.00%      
Threshold percentage of stock price trigger 130.00%      
Threshold trading days | day 20      
Threshold consecutive trading days | day 3      
Conversion notice period 30 days