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 6 Months Ended
Nov. 30, 2018
Nov. 30, 2017
Nov. 30, 2018
Nov. 30, 2017
JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]        
Line of Credit Facility [Line Items]        
Number of days borrowed 4 days 6 days 10 days 19 days
Maximum amount borrowed $ 483.0 $ 700.0 $ 483.0 $ 700.0
Weighted-average amount borrowed $ 389.8 $ 445.8 $ 285.7 $ 331.6
Weighted-average interest rate 5.12% 4.25% 5.06% 4.24%
JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]        
Line of Credit Facility [Line Items]        
Number of days borrowed 3 days 20 days 7 days 20 days
Maximum amount borrowed $ 135.5 $ 400.0 $ 223.0 $ 400.0
Weighted-average amount borrowed $ 83.0 $ 215.8 $ 111.8 $ 215.8
Weighted-average interest rate 5.25% 2.84% 5.07% 2.84%
PNC $150 Million Credit Facility [Member] | PNC Bank, National Association [Member]        
Line of Credit Facility [Line Items]        
Number of days borrowed 91 days 91 days 179 days 179 days
Maximum amount borrowed $ 57.7 $ 58.6 $ 57.7 $ 58.6
Weighted-average amount borrowed $ 57.3 $ 57.8 $ 56.6 $ 56.8
Weighted-average interest rate 2.68% 1.78% 2.61% 1.73%