CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jan. 31, 2013	Apr. 30, 2012
Allowance for doubtful accounts	$ 11,027	$ 9,437
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000	150,000
Common stock, shares issued	60,912	59,975
Common stock, shares outstanding	48,630	47,913