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           Business combinations (Details 2) (USD $) 
        In Thousands, unless otherwise specified  | 
        0 Months Ended | 12 Months Ended | 0 Months Ended | |
|---|---|---|---|---|
| 
           Jul. 02, 2013 
         | 
        
           Sep. 30, 2014
 
          HML 
         | 
        
           Jul. 02, 2013
 
          HML
 
          Customer relationships 
         | 
        
           Jul. 02, 2013
 
          HML
 
          Technology-based intangible assets 
         | 
      |
| Intangible assets acquired | ||||
| Useful life | 19 years 6 months | 20 years | 2 years | |
| Fair value | $ 20,542 | $ 19,933 | $ 609 | |
| X | ||||||||||
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- Details 
          
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- Definition 
          Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, resulting from a business combination. No definition available. 
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