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Commitments and Contingencies (Details) - USD ($)
$ in Millions
Jan. 31, 2020
Apr. 30, 2019
Concentration Risk [Line Items]    
Accounts Receivable, after Allowance for Credit Loss, Current $ 732 $ 609
Credit Concentration Risk [Member]    
Concentration Risk [Line Items]    
Guaranty exposure, maximum 10  
Guaranty exposure, current 6  
Accounts Receivable, after Allowance for Credit Loss, Current $ 13