Stock Repurchase Program - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Feb. 29, 2016 USD ($) shares	Feb. 29, 2016 USD ($) shares
Stock Repurchase Programs [Line Items]
Authorization of stock repurchase program		Jan. 08, 2008
Shares repurchased	400,000	800,000
Shares repurchased, value | $	$ 17.8	$ 35.1
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