Stock Repurchase Program - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Stock Repurchase Programs [Line Items]
Authorization of stock repurchase program			Jan. 08, 2008
Shares repurchased	0	0	0	0
Minimum
Stock Repurchase Programs [Line Items]
Shares authorized to be repurchased, per year	1,000,000		1,000,000
Maximum
Stock Repurchase Programs [Line Items]
Shares authorized to be repurchased, per year	2,000,000		2,000,000