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Stock-Based Compensation (Details) - Schedule of stock-based compensation - USD ($)
$ in Millions
3 Months Ended
Aug. 31, 2016
Aug. 31, 2015
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]    
Stock-based compensation expense $ 1.6 $ 1.4
Share-based payment awards, options, by number of shares issued from Treasury Stock 200,000.0 1,000,000.0
Employee Stock Expense    
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]    
Stock-based compensation expense $ 0.8 $ 0.7
Restricted Stock Unit Expense    
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]    
Stock-based compensation expense 0.7 0.6
Management Stock Purchase Plan    
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]    
Stock-based compensation expense 0.0 0.0
Employee Stock Purchase Plan    
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]    
Stock-based compensation expense $ 0.1 $ 0.1