Summary of Non-Vested Stock Option Awards (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	May 31, 2012
Number of Stock Options
Non-vested, beginning of year	3,935
Granted	600
Vested	(1,160)
Forfeited	(268)
Non-vested, end of year	3,107
Weighted Average Grant Date Fair Value Per Share
Non-vested, beginning of year	$ 5.14
Granted	$ 7.50
Vested	$ 5.29
Forfeited	$ 5.36
Non-vested, end of year	$ 5.52