Annual report pursuant to Section 13 and 15(d)

Short-term Financing (Narrative) (Details)

v3.10.0.1
Short-term Financing (Narrative) (Details)
$ in Millions
 12 Months Ended
Jun. 01, 2018
USD ($)
May 31, 2018
USD ($)
May 31, 2017
USD ($)
Aug. 17, 2017
USD ($)
loan
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   $ 700.0 $ 450.0  
Number of days borrowed   22 days 30 days  
Weighted-average interest rate   4.27% 2.89%  
Weighted-average amount borrowed   $ 319.1 $ 196.7  
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    
Weighted-average interest rate   4.25%    
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Seven Days [Member]        
Line of Credit Facility [Line Items]        
Maximum amount borrowed     $ 150.0  
Number of days borrowed     7 days  
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Eighteen Days [Member]        
Line of Credit Facility [Line Items]        
Maximum amount borrowed     $ 50.0  
Number of days borrowed     18 days  
Revolving Credit Facility [Member] | JPM $1 Billion Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Seven And Eighteen Days [Member] | LIBOR [Member]        
Line of Credit Facility [Line Items]        
Weighted-average interest rate     1.40%  
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 $ 171.8      
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    
Maximum amount borrowed   $ 400.0    
Number of days borrowed   42 days    
Weighted-average interest rate   2.80%    
Weighted-average amount borrowed   $ 144.8    
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Seven Days [Member]        
Line of Credit Facility [Line Items]        
Maximum amount borrowed   $ 300.0    
Number of days borrowed   7 days    
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Seven Days [Member] | LIBOR [Member]        
Line of Credit Facility [Line Items]        
Weighted-average interest rate   2.13%    
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Thirty Days [Member]        
Line of Credit Facility [Line Items]        
Maximum amount borrowed   $ 75.0    
Number of days borrowed   30 days    
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Thirty Days [Member] | LIBOR [Member]        
Line of Credit Facility [Line Items]        
Weighted-average interest rate   2.19%    
Revolving Credit Facility [Member] | JPM $500 Million Credit Facility [Member] | JP Morgan Chase Bank, N.A. [Member] | Three Overnight Basis [Member] | Subsequent Event [Member]        
Line of Credit Facility [Line Items]        
Weighted-average amount borrowed 103.5      
Revolving Credit Facility [Member] | PNC $150 Million Credit Facility [Member] | PNC Bank, National Association [Member]        
Line of Credit Facility [Line Items]        
Amounts outstanding   $ 0.0 $ 0.0  
Maximum amount borrowed   $ 59.9 $ 55.6  
Number of days borrowed   358 days 353 days  
Weighted-average interest rate   1.94% 1.21%  
Weighted-average amount borrowed   $ 57.2 $ 52.8  
Revolving Credit Facility [Member] | PNC $150 Million Credit Facility [Member] | PNC Bank, National Association [Member] | Subsequent Event [Member]        
Line of Credit Facility [Line Items]        
Amounts outstanding 56.8      
Standby Letters of Credit [Member]        
Line of Credit Facility [Line Items]        
Maximum borrowing capacity   56.8 47.3  
Amounts outstanding   0.0 0.0  
Standby Letters of Credit [Member] | Extended Maturity [Member] | Subsequent Event [Member]        
Line of Credit Facility [Line Items]        
Maximum borrowing capacity $ 60.9      
Expiration Date Jul. 01, 2019      
Increase amount available $ 4.1      
Line of Credit [Member]        
Line of Credit Facility [Line Items]        
Number of terminated lines of credit | loan       4
Amounts outstanding   $ 0.0 $ 0.0  
Maximum borrowing capacity       $ 900.0
Minimum [Member] | Standby Letters of Credit [Member]        
Line of Credit Facility [Line Items]        
Expiration Date   Jul. 01, 2018    
Maximum [Member] | Standby Letters of Credit [Member]        
Line of Credit Facility [Line Items]        
Expiration Date   May 01, 2019