Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Number of Options
Beginning balance	12,083	11,691
Options granted	5,053	2,932
Options exercised	(4,597)	(1,677)
Options forfeited	(1,710)	(863)
Ending balance	10,829	12,083
Ending balance	5,481
Weighted Average Exercise Price
Beginning balance	$ 4.57	$ 3.02
Options granted	$ 8.43	$ 9.41
Options exercised	$ 2.45	$ 1.82
Options forfeited	$ 7.49	$ 5.33
Ending balance	$ 6.83	$ 4.57
Ending balance	$ 4.12