Quarterly report pursuant to Section 13 or 15(d)

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

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Description of Business, Basis of Presentation, and Significant Accounting Policies (Details) - USD ($)
$ in Millions
2 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Feb. 29, 2016
Feb. 29, 2016
Feb. 28, 2015
Feb. 29, 2016
Feb. 28, 2015
May. 31, 2015
Dec. 31, 2014
Description of Business, Basis of Presentation, and Significant Accounting Policies (Textual)              
Disclosure on geographic areas, Description of revenue from external customers       revenue within Germany, which represented less than one percent of the Company's total revenue revenue within Germany, which represented less than one percent of the Company's total revenue    
Disclosure on geographic areas, Long-lived assets       Long-lived assets in Germany are insignificant in relation to total long-lived assets of the Company   Long-lived assets in Germany are insignificant in relation to total long-lived assets of the Company  
Allowance for doubtful accounts $ 4.1 $ 4.1   $ 4.1   $ 1.4  
Trade accounts receivable, net 175.4 175.4   175.4   176.6  
Purchased accounts receivable, net 178.0 178.0   178.0      
Maximum individual workers' compensation claims liability       1.3   $ 1.0  
Maximum individual claims liability health insurance $ 0.3           $ 0.3
Stock-based compensation costs recognized   $ 8.6 $ 8.6 $ 26.1 $ 24.0