Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Oct. 31, 2016	Apr. 30, 2016
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 805	$ 680
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	71,839,096	71,558,633
Common stock, shares outstanding	56,276,463	55,996,011
Treasury stock, shares	15,562,622	15,562,622