| 
           Acquisitions (Tables)
  
         | 
        12 Months Ended | 
      
      
        | 
           Sep. 30, 2012 
         | 
      
      
        | 
           Policy Studies, Inc 
         | 
         
 | 
      
      
        | Acquisition Disclosures | 
         
 | 
      
      
        | Assets and liabilities recorded in the Company's financial statements at their fair values as of the date of the acquisition | 
        
| 
   
  
| 
   
 | 
   
 | 
 Preliminary Purchase Price Allocation 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 As of June 30, 2012 
 | 
   
 | 
 Adjustments 
 | 
   
 | 
 As of September 30, 2012 
 | 
   
 | 
 
| 
 Accounts receivable and unbilled receivables 
 | 
   
 | 
 $ 
 | 
 22,875 
 | 
   
 | 
 $ 
 | 
 142 
 | 
   
 | 
 $ 
 | 
 23,017 
 | 
   
 | 
 
| 
 Other current assets 
 | 
   
 | 
 9,527 
 | 
   
 | 
 — 
 | 
   
 | 
 9,527 
 | 
   
 | 
 
| 
 Deferred income taxes 
 | 
   
 | 
 2,629 
 | 
   
 | 
 (698 
 | 
 ) 
 | 
 1,931 
 | 
   
 | 
 
| 
 Property and equipment 
 | 
   
 | 
 6,411 
 | 
   
 | 
 — 
 | 
   
 | 
 6,411 
 | 
   
 | 
 
| 
 Other assets 
 | 
   
 | 
 1,332 
 | 
   
 | 
 — 
 | 
   
 | 
 1,332 
 | 
   
 | 
 
| 
 Intangible assets 
 | 
   
 | 
 22,883 
 | 
   
 | 
 (700 
 | 
 ) 
 | 
 22,183 
 | 
   
 | 
 
| 
 Total identifiable assets acquired 
 | 
   
 | 
 65,657 
 | 
   
 | 
 (1,256 
 | 
 ) 
 | 
 64,401 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Accounts payable and other liabilities 
 | 
   
 | 
 20,845 
 | 
   
 | 
 (179 
 | 
 ) 
 | 
 20,666 
 | 
   
 | 
 
| 
 Deferred revenue 
 | 
   
 | 
 5,752 
 | 
   
 | 
 13,944 
 | 
   
 | 
 19,696 
 | 
   
 | 
 
| 
 Deferred taxation 
 | 
   
 | 
 7,537 
 | 
   
 | 
 (7,537 
 | 
 ) 
 | 
 — 
 | 
   
 | 
 
| 
 Total liabilities assumed 
 | 
   
 | 
 34,134 
 | 
   
 | 
 6,228 
 | 
   
 | 
 40,362 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Net identifiable assets acquired 
 | 
   
 | 
 31,523 
 | 
   
 | 
 (7,484 
 | 
 ) 
 | 
 24,039 
 | 
   
 | 
 
| 
 Goodwill 
 | 
   
 | 
 32,705 
 | 
   
 | 
 6,456 
 | 
   
 | 
 39,161 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Net assets acquired 
 | 
   
 | 
 $ 
 | 
 64,228 
 | 
   
 | 
 $ 
 | 
 (1,028 
 | 
 ) 
 | 
 $ 
 | 
 63,200 
 | 
   
 | 
 
 
  
 | 
 
 
 | 
      
      
        | Valuation of the Intangible Assets Acquired | 
        
| 
   
  
| 
   
 | 
   
 | 
 Useful life 
 | 
   
 | 
 Fair value 
 | 
   
 | 
 
| 
 Customer relationships 
 | 
   
 | 
 7-8 years 
 | 
   
 | 
 $ 
 | 
 16,600 
 | 
   
 | 
 
| 
 Tradename 
 | 
   
 | 
 5 years 
 | 
   
 | 
 3,800 
 | 
   
 | 
 
| 
 Technology-based intangible assets 
 | 
   
 | 
 1-5 years 
 | 
   
 | 
 1,783 
 | 
   
 | 
 
| 
 Total intangible assets 
 | 
   
 | 
   
 | 
   
 | 
 $ 
 | 
 22,183 
 | 
   
 | 
 
 
 | 
 
 
 | 
      
      
        | Schedule of Pro forma information relating to the acquisition | 
        
| 
   
  
| 
   
 | 
   
 | 
 Unaudited pro forma results 
for the year ended 
September 30, 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2012 
 | 
   
 | 
 2011 
 | 
   
 | 
 
| 
 Revenue 
 | 
   
 | 
 $ 
 | 
 1,132,177 
 | 
   
 | 
 $ 
 | 
 1,065,345 
 | 
   
 | 
 
| 
 Income from continuing operations 
 | 
   
 | 
 75,252 
 | 
   
 | 
 82,993 
 | 
   
 | 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
 
 | 
 
 
 | 
      
      
        | 
           DeltaWare 
         | 
         
 | 
      
      
        | Acquisition Disclosures | 
         
 | 
      
      
        | Assets and liabilities recorded in the Company's financial statements at their fair values as of the date of the acquisition | 
        
| 
   
  
| 
   
 | 
   
 | 
 Purchase 
price 
allocation 
 | 
   
 | 
 
| 
 Cash, net of cash acquired 
 | 
   
 | 
 $ 
 | 
 10,385 
 | 
   
 | 
 
| 
 Contingent consideration obligations  
 | 
   
 | 
 3,015 
 | 
   
 | 
 
| 
 Total fair value of consideration  
 | 
   
 | 
 $ 
 | 
 13,400 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Accounts receivable  
 | 
   
 | 
 $ 
 | 
 2,010 
 | 
   
 | 
 
| 
 Other tangible assets  
 | 
   
 | 
 1,571 
 | 
   
 | 
 
| 
 Intangible assets  
 | 
   
 | 
 6,060 
 | 
   
 | 
 
| 
 Total identifiable assets acquired  
 | 
   
 | 
 9,641 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Accounts payable and other liabilities  
 | 
   
 | 
 2,125 
 | 
   
 | 
 
| 
 Loans payable  
 | 
   
 | 
 870 
 | 
   
 | 
 
| 
 Deferred revenue  
 | 
   
 | 
 723 
 | 
   
 | 
 
| 
 Total liabilities assumed  
 | 
   
 | 
 3,718 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Net identifiable assets acquired  
 | 
   
 | 
 5,923 
 | 
   
 | 
 
| 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Goodwill  
 | 
   
 | 
 7,477 
 | 
   
 | 
 
| 
 Net assets acquired  
 | 
   
 | 
 $ 
 | 
 13,400 
 | 
   
 | 
 
 
 | 
 
 
 | 
      
      
        | Schedule of the effect on the financial statements of acquisition-related contingent consideration | 
        
| 
   
  
| 
   
 | 
   
 | 
 Contingent 
consideration 
 | 
   
 | 
 
| 
 Balance at September 30, 2011 
 | 
   
 | 
 $ 
 | 
 2,228 
 | 
   
 | 
 
| 
 Additional estimated consideration  
 | 
   
 | 
 101 
 | 
   
 | 
 
| 
 Payment of consideration  
 | 
   
 | 
 (2,059 
 | 
 ) 
 | 
 
| 
 Foreign currency translation  
 | 
   
 | 
 136 
 | 
   
 | 
 
| 
 Balance at September 30, 2012  
 | 
   
 | 
 $ 
 | 
 406 
 | 
   
 | 
 
 
 | 
 
 
 | 
      
      
        | Valuation of the Intangible Assets Acquired | 
        
| 
   
  
| 
   
 | 
   
 | 
 Useful life 
 | 
   
 | 
 Fair value 
 | 
   
 | 
 
| 
 Technology-based intangibles  
 | 
   
 | 
 8.5 years 
 | 
   
 | 
 $ 
 | 
 3,733 
 | 
   
 | 
 
| 
 Customer contracts and relationships  
 | 
   
 | 
 8-10 years 
 | 
   
 | 
 1,474 
 | 
   
 | 
 
| 
 Non-compete arrangements  
 | 
   
 | 
 4 years 
 | 
   
 | 
 239 
 | 
   
 | 
 
| 
 Trade name  
 | 
   
 | 
 10 years 
 | 
   
 | 
 614 
 | 
   
 | 
 
| 
 Total intangible assets  
 | 
   
 | 
   
 | 
   
 | 
 $ 
 | 
 6,060 
 | 
   
 | 
 
 
 | 
 
 
 |