Computation of Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Aug. 31, 2014	Aug. 31, 2013
Denominator:
Denominator for basic earnings per share - weighted average common shares outstanding (including shares issuable for vested restricted stock units)	24,372	24,291
Effect of unvested restricted stock units	24	37
Diluted shares used in per share calculation	24,396	24,328
Net income	$ 4,771	$ 5,697
Earnings per share:
Basic (in dollars per share)	$ 0.20	$ 0.23
Diluted (in dollars per share)	$ 0.20	$ 0.23
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	69	0