Stock Repurchase Program - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
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