Annual report pursuant to Section 13 and 15(d)

Description of Business and Significant Accounting Policies (Details)

 v2.3.0.11
Description of Business and Significant Accounting Policies (Details) (USD $)
 12 Months Ended
May 31, 2011
May 31, 2010
May 31, 2009
Description of Business and Significant Accounting Policies (Textuals) [Abstract]      
Net of allowance for doubtful accounts $ 2,100,000 $ 1,900,000  
Minimum period of amortized intangible assets, in years 5    
Maximum period of amortized intangible assets, in years 12    
Direct costs billed and incurred 3,900,000,000 3,100,000,000 2,600,000,000
Period in which payroll taxes typically remitted, after receipt of collections from client one to 30 days    
Maximum period payroll taxes remitted, after receipt of collections from client 90 days    
Maximum individual workers' compensation claims liability 1,000,000 1,000,000  
Workers' compensation insurance claims in current liabilities 7,300,000 5,800,000  
Workers' compensation insurance claims in long-term liabilities 20,600,000 20,100,000  
Total reserve for uncertain tax positions $ 34,400,000 $ 27,500,000  
Buildings and improvements [Member]
      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Useful Life, in years, Minimum 10    
Property, Plant and Equipment, Useful Life, in years, Maximum 35    
Data processing equipment [Member]
      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Useful Life, in years, Minimum 2    
Property, Plant and Equipment, Useful Life, in years, Maximum 7    
Furniture, fixtures and equipment [Member]
      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Useful Life, in years, Maximum 7    
Leasehold improvements [Member]
      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Useful Life, in years, Maximum 10    
Software development costs [Member]
      
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Useful Life, in years, Minimum 3    
Property, Plant and Equipment, Useful Life, in years, Maximum 15