Quarterly report pursuant to Section 13 or 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
 3 Months Ended
Aug. 31, 2018
Aug. 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 6 days 13 days
Maximum amount borrowed $ 394.5 $ 660.0
Weighted-average amount borrowed $ 216.3 $ 278.8
Weighted-average interest rate 4.99% 4.23%
JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 4 days  
Maximum amount borrowed $ 223.0  
Weighted-average amount borrowed $ 133.4  
Weighted-average interest rate 4.99% 0.00%
PNC $150 Million Credit Facility [Member] | PNC Bank, National Association [Member]    
Line of Credit Facility [Line Items]    
Number of days borrowed 88 days 88 days
Maximum amount borrowed $ 56.8 $ 57.2
Weighted-average amount borrowed $ 56.0 $ 55.8
Weighted-average interest rate 2.53% 1.67%