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Subsequent Events (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 12 Months Ended
Jul. 31, 2018
Jul. 31, 2017
May 22, 2018
Subsequent Event [Line Items]      
Business Divestiture Revenue   $ 16  
Subsequent Event [Member]      
Subsequent Event [Line Items]      
Proceeds from Divestiture of Businesses $ 20    
Dividend declared (USD per share)     $ 0.2075