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           Business and summary of significant accounting policies (Details 4) 
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        12 Months Ended | 
|---|---|
| 
           Sep. 30, 2012 
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      |
| Components of intangible assets | |
| Estimated useful lives of customer contracts and relationships, technology-based intangibles and non-competition agreements | 6 years 3 months 18 days | 
| 
           Minimum 
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        |
| Components of intangible assets | |
| Estimated useful lives of customer contracts and relationships, technology-based intangibles and non-competition agreements | 1 year | 
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           Maximum 
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        |
| Components of intangible assets | |
| Estimated useful lives of customer contracts and relationships, technology-based intangibles and non-competition agreements | 10 years | 
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- Details 
          
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- Definition 
          Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. No definition available. 
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