| 
           Capitalized software (Details) (USD $) 
         | 
        12 Months Ended | ||
|---|---|---|---|
| 
           Sep. 30, 2014 
         | 
        
           Sep. 30, 2013 
         | 
        
           Sep. 30, 2012 
         | 
      |
| Capitalized software | |||
| Capitalized software | $ 72,758,000 | $ 64,189,000 | |
| Less: Accumulated amortization | (33,024,000) | (23,733,000) | |
| Total Software development costs, net | 39,734,000 | 40,456,000 | |
| Capitalized software amortization expense | $ 9,900,000 | $ 4,600,000 | $ 4,900,000 | 
| X | ||||||||||
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- Definition 
          For each balance sheet presented, the amount of accumulated amortization for capitalized computer software costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          For each income statement presented, the amount charged to expense for amortization of capitalized computer software costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
          
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