Quarterly report pursuant to Section 13 or 15(d)

Basic and Diluted Earnings Per Share (Narrative) (Details)

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Basic and Diluted Earnings Per Share (Narrative) (Details) - USD ($)
shares in Millions, $ in Millions
 3 Months Ended 9 Months Ended
Feb. 28, 2018
Feb. 28, 2017
Feb. 28, 2018
Feb. 28, 2017
Authorized in May 2014 [Member]        
Equity, Class of Treasury Stock [Line Items]        
Common stock repurchased and retired, values       $ 59.7
Authorized in July 2016 [Member]        
Equity, Class of Treasury Stock [Line Items]        
Expiration date     May 31, 2019  
Approved repurchase amount $ 350.0   $ 350.0  
Common stock repurchased and retired, shares 0.0 0.0 1.6 2.9
Common stock repurchased and retired, values     $ 94.1 $ 166.2
Common Stock [Member]        
Equity, Class of Treasury Stock [Line Items]        
Common stock issued in connection with exercise or vesting of stock-based awards 0.1 0.4 0.9 1.8
Common stock issued related to acquisition     0.6