Reconciliation of Denominator Used in Computation of Basic and Diluted Earnings per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2013	Nov. 30, 2012
Denominator:
Denominator for basic earnings per share - weighted average common shares outstanding (including shares issuable for vested restricted stock units)	24,331	23,988	24,313	23,994
Effect of unvested restricted stock units	19	237	27	227
Diluted shares used in per share calculation	24,350	24,225	24,340	24,221
Net income	$ 5,581	$ 6,239	$ 11,278	$ 11,325
Earnings per share:
Basic	$ 0.23	$ 0.26	$ 0.46	$ 0.47
Diluted	$ 0.23	$ 0.26	$ 0.46	$ 0.47