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, 2018
Sep. 30, 2017
Components of intangible assets    
Cost $ 139,359 $ 142,093
Accumulated Amortization 51,324 43,324
Intangible Assets, net 88,035 98,769
Customer contracts and relationships    
Components of intangible assets    
Cost 129,113 129,916
Accumulated Amortization 42,683 33,457
Intangible Assets, net 86,430 96,459
Technology-based intangible assets    
Components of intangible assets    
Cost 5,750 7,664
Accumulated Amortization 4,212 5,475
Intangible Assets, net 1,538 2,189
Trademarks and trade names    
Components of intangible assets    
Cost 4,496 4,513
Accumulated Amortization 4,429 4,392
Intangible Assets, net $ 67 $ 121
Weighted Average    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 11 years 11 months  
Weighted Average | Customer contracts and relationships    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 12 years  
Weighted Average | Technology-based intangible assets    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 5 years  
Weighted Average | Trademarks and trade names    
Components of intangible assets    
Weighted average remaining life of assets not fully amortized 1 year 4 months