Computation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Denominator:
Denominator for basic earnings per share - weighted average common shares outstanding (including shares issuable for vested restricted stock units)	24,416	24,372
Effect of unvested restricted stock units	10	24
Diluted shares used in per share calculation	24,426	24,396
Net income	$ 2,470	$ 4,771
Earnings per share:
Basic (in dollars per share)	$ 0.10	$ 0.20
Diluted (in dollars per share)	$ 0.10	$ 0.20
Antidilutive securities excluded from computation of earnings per share (shares)	146	69