Annual report pursuant to Section 13 and 15(d)

Goodwill and intangible assets - Schedule of Finite-Lived Intangible Assets (Details)

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Goodwill and intangible assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Components of intangible assets    
Cost $ 142,093 $ 143,675
Accumulated Amortization 43,324 34,648
Intangible Assets, net 98,769 109,027
Customer contracts and relationships    
Components of intangible assets    
Cost 129,916 132,221
Accumulated Amortization 33,457 26,238
Intangible Assets, net 96,459 105,983
Technology-based intangible assets    
Components of intangible assets    
Cost 7,664 6,967
Accumulated Amortization 5,475 4,613
Intangible Assets, net 2,189 2,354
Trademarks and trade names    
Components of intangible assets    
Cost 4,513 4,487
Accumulated Amortization 4,392 3,797
Intangible Assets, net $ 121 $ 690
Weighted Average    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 12 years 6 months  
Weighted Average | Customer contracts and relationships    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 12 years 8 months  
Weighted Average | Technology-based intangible assets    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 5 years 2 months  
Weighted Average | Trademarks and trade names    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 2 years 3 months