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Stock-Based Compensation (Tables)
9 Months Ended
Feb. 29, 2012
Non-Qualified Stock Options [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Assumptions To Value Stock Options

Dividend yield

     2.7  

Expected volatility

     51.7  

Risk-free interest rate

     1.9  

Expected term (years)

     6.0     
Market-Based Restricted Common Shares [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Assumptions To Value Stock Options

Dividend yield

     2.3

Expected volatility

     52.6

Risk-free interest rate

     1.8