Business, Basis of Presentation and Summary of Significant Accounting Policies - Authorized Shares of Stock and Stock Split (Details) shares in Thousands	May 13, 2016 $ / shares shares	Jan. 31, 2018 $ / shares shares	Apr. 30, 2017 $ / shares shares
Stock
Stock authorized (in shares)	550,000
Common stock authorized (in shares)	500,000	500,000	500,000
Preferred stock authorized (in shares)	50,000	50,000	50,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01	$ 0.01
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01	$ 0.01
Common Stock
Stock
Stock split ratio	10.158