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 6 Months Ended 12 Months Ended
Nov. 30, 2011
Nov. 30, 2010
Nov. 30, 2011
Nov. 30, 2010
May 31, 2012
May 31, 2011
Description of Business and Significant Accounting Policies (Textuals) [Abstract]            
Direct costs billed and incurred $ 873.1 $ 1,000.0 $ 1,800.0 $ 2,000.0    
Maximum individual workers' compensation claims liability         1.0 1.0
Workers' compensation insurance claims in current liabilities 7.3   7.3     7.3
Workers' compensation insurance claims in long-term liabilities 19.1   19.1     20.6
Stock based compensation costs recognized $ 5.3 $ 6.4 $ 11.9 $ 13.5