XML 73 R61.htm IDEA: XBRL DOCUMENT v3.3.1.900
Stock Plans (Schedule of estimated fair value of stock options granted and the assumptions used for the Black-Scholes option-pricing model) (Details) - $ / shares
9 Months Ended
Feb. 28, 2016
Feb. 22, 2015
Stock Plans [Abstract]    
Estimated fair values of stock options granted $ 7.24 $ 7.22
Assumptions:    
Risk-free interest rate 2.40% 2.60%
Expected term 8 years 6 months 8 years 6 months
Expected volatility 17.60% 17.50%
Dividend yield 3.20% 3.00%