Quarterly report pursuant to Section 13 or 15(d)

Description of Business and Significant Accounting Policies (Details Textuals)

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Description of Business and Significant Accounting Policies (Details Textuals) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Aug. 31, 2011
Aug. 31, 2010
May 31, 2012
May 31, 2011
Description of Business and Significant Accounting Policies (Textuals) [Abstract]        
Direct costs billed and incurred $ 891.5 $ 950.9    
Maximum individual workers' compensation claims liability     1.0 1.0
Workers' compensation insurance claims in current liabilities 7.6     7.3
Workers' compensation insurance claims in long-term liabilities 17.6     20.6
Stock based compensation costs recognized 6.6 7.1    
Total unrecognized compensation cost related to all unvested stock-based awards $ 60.9      
weighted average period for unrecognized compensation cost 3.3