Calculation of Basic and Diluted EPS (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Summary Of Significant Accounting Policies [Abstract]
Net income (loss)	$ 7,476	$ (64,913)	$ (38,853)
Unvested restricted share participation	(14)	31	16
Income (loss) allocated to common shareholders	$ 7,462	$ (64,882)	$ (38,837)
Weighted-average shares outstanding	27,927	27,836	27,752
Contingently issuable shares	2	2	6
Unvested restricted shares	(15)	(13)	(14)
Basic weighted-average shares	27,914	27,825	27,744
Stock option, restricted share and award dilution	102
Diluted weighted-average shares	28,016	27,825	27,744
Basic	$ 0.27	$ (2.33)	$ (1.40)
Diluted	$ 0.27	$ (2.33)	$ (1.40)