Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Short-term Financing (Credit Facility Amount Borrowed) (Details) - Revolving Credit Facility [Member] - USD ($)
$ in Millions
12 Months Ended
May 31, 2018
May 31, 2017
JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 22 days 30 days
Maximum amount borrowed $ 700.0 $ 450.0
Weighted-average amount borrowed $ 319.1 $ 196.7
Weighted-average interest rate 4.27% 2.89%
JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 42 days  
Maximum amount borrowed $ 400.0  
Weighted-average amount borrowed $ 144.8  
Weighted-average interest rate 2.80%  
PNC $150 Million Credit Facility [Member] | PNC Bank, National Association [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 358 days 353 days
Maximum amount borrowed $ 59.9 $ 55.6
Weighted-average amount borrowed $ 57.2 $ 52.8
Weighted-average interest rate 1.94% 1.21%