Summary of Significant Accounting Policies and Practices - Amounts Used In Basic and Diluted Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted-average number of basic shares outstanding	21,193	20,645	20,781	20,574
Stock options, stock units and performance awards	228	442	284	497
Conversion of non-controlling interest		757	362	757
Total shares and dilutive securities	21,421	21,844	21,427	21,828