Quarterly report pursuant to Section 13 or 15(d)

Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)

v3.6.0.2
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Nov. 30, 2016
USD ($)
Nov. 30, 2015
USD ($)
Nov. 30, 2016
USD ($)
segment
$ / shares
Nov. 30, 2015
USD ($)
May 31, 2016
USD ($)
May 31, 2015
USD ($)
Accounting Policies [Line Items]            
State of incorporation     Delaware      
Number of reportable segments | segment     1      
Allowance for doubtful accounts $ 6.0   $ 6.0   $ 4.2  
Accounts receivable, net of allowance for doubtful accounts 528.9   528.9   408.6  
Maximum individual workers' compensation claims liability     1.3   1.3  
Maximum individual health insurance claims liability     0.3     $ 0.3
Stock-based compensation costs recognized 8.5 $ 8.7 17.6 $ 17.5    
Excess tax benefit in income tax expense     $ 14.1      
Diluted earnings per share increase | $ / shares     $ 0.04      
Trade Receivables [Member]            
Accounting Policies [Line Items]            
Accounts receivable, net of allowance for doubtful accounts 295.0   $ 295.0   221.6  
Purchased Receivables [Member]            
Accounting Policies [Line Items]            
Accounts receivable, net of allowance for doubtful accounts $ 233.9   $ 233.9   $ 187.0  
Germany [Member] | Total Revenue [Member] | Geographic Concentration Risk [Member]            
Accounting Policies [Line Items]            
Percentage of total revenue less than one percent     1.00% 1.00%