Quarterly report pursuant to Section 13 or 15(d)

Short-term Financing (Narrative) (Details)

v3.8.0.1
Short-term Financing (Narrative) (Details)
$ in Millions
 3 Months Ended
Sep. 01, 2017
USD ($)
Aug. 31, 2017
USD ($)
Aug. 31, 2016
USD ($)
Aug. 17, 2017
USD ($)
loan
May 31, 2017
USD ($)
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]          
Line of Credit Facility [Line Items]          
Amounts outstanding   $ 0.0     $ 0.0
Maximum amount borrowed   $ 660.0 $ 350.0    
Number of days borrowed   13 days 4 days    
Weighted-average interest rate   4.23% 3.50%    
Weighted-average amount borrowed   $ 278.8 $ 237.5    
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Three Days [Member]          
Line of Credit Facility [Line Items]          
Maximum amount borrowed   $ 100.0      
Number of days borrowed   3 days      
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Three Days [Member] | LIBOR [Member]          
Line of Credit Facility [Line Items]          
Weighted-average interest rate   4.25%      
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Two Overnight Basis [Member] | Subsequent Event [Member]          
Line of Credit Facility [Line Items]          
Weighted-average amount borrowed $ 650.0        
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member]          
Line of Credit Facility [Line Items]          
Amounts outstanding   $ 0.0      
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Two Overnight Basis [Member] | Subsequent Event [Member]          
Line of Credit Facility [Line Items]          
Weighted-average amount borrowed $ 212.5        
Revolving Credit Facility [Member] | PNC $150 Million Credit Facility [Member] | PNC Bank, National Association [Member]          
Line of Credit Facility [Line Items]          
Amounts outstanding   57.2     0.0
Maximum amount borrowed   $ 57.2 $ 51.3    
Number of days borrowed   88 days 84 days    
Weighted-average interest rate   1.67% 1.01%    
Weighted-average amount borrowed   $ 55.8 $ 51.3    
Standby Letters of Credit [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity   52.8     47.3
Amounts outstanding   0.0 0.0   0.0
Line of Credit [Member]          
Line of Credit Facility [Line Items]          
Number of terminated lines of credit | loan       4  
Amounts outstanding   $ 0.0 $ 0.0   $ 0.0
Maximum borrowing capacity       $ 900.0  
Minimum [Member] | Standby Letters of Credit [Member]          
Line of Credit Facility [Line Items]          
Expiration Date   Dec. 01, 2017      
Maximum [Member] | Standby Letters of Credit [Member]          
Line of Credit Facility [Line Items]          
Expiration Date   Jul. 01, 2018