CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Oct. 31, 2018	Apr. 30, 2018
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 20,197	$ 17,845
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	72,202,000	71,631,000
Common stock, shares outstanding	56,511,000	56,517,000