CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Apr. 30, 2016	Apr. 30, 2015
Allowance for doubtful accounts	$ 11,292	$ 9,958
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	69,723,000	62,863,000
Common stock, shares outstanding	57,272,000	50,573,000