Shareholders' Equity (Details) (USD $)	3 Months Ended
	Aug. 31, 2014	Aug. 31, 2013
Class of Stock [Line Items]
Repurchase of common stock (in shares)	1,800,000.0	3,100,000.0
Repurchase of common stock	$ 124,492,000	$ 144,397,000
Repurchase of common stock, average price per share	$ 69.82	$ 47.33
Remaining authorized repurchase amount	245,100,000.0
Other Than Accelerated Share Repurchase Program [Member]
Class of Stock [Line Items]
Repurchase of common stock	$ 124,500,000	$ 144,400,000