Stock Repurchase Program - Additional Information (Detail) $ in Millions	3 Months Ended
	Aug. 31, 2015 USD ($) shares
Stock Repurchase Programs [Line Items]
Authorization of stock repurchase program	Jan. 08, 2008
Shares repurchased	300,000
Shares repurchased, value | $	$ 12.8
Minimum
Stock Repurchase Programs [Line Items]
Shares authorized to be repurchased, per year	1,000,000
Maximum
Stock Repurchase Programs [Line Items]
Shares authorized to be repurchased, per year	2,000,000