Annual report pursuant to Section 13 and 15(d)

Short-term Financing (Lines of Credit Facility Amount Borrowed) (Details)

v3.7.0.1
Short-term Financing (Lines of Credit Facility Amount Borrowed) (Details) - Revolving Credit Facility [Member] - USD ($)
$ in Millions
12 Months Ended
May 31, 2017
May 31, 2016
JP Morgan Chase Bank, N.A. [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 30 days 5 days
Maximum amount borrowed $ 450.0 $ 450.0
Weighted-average amount borrowed $ 196.7 $ 305.0
Weighted-average interest rate 2.89% 3.39%
PNC Bank, National Association [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 353 days  
Maximum amount borrowed $ 55.6  
Weighted-average amount borrowed $ 52.8  
Weighted-average interest rate 1.21%