Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Nov. 30, 2017
USD ($)
Nov. 30, 2016
USD ($)
Nov. 30, 2017
USD ($)
segment
Nov. 30, 2016
USD ($)
May 31, 2017
USD ($)
Accounting Policies [Line Items]          
Number of reportable segments | segment     1    
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 $ 10.4 $ 8.5 $ 19.1 $ 17.6  
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%