Operations and summary of significant accounting policies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended	36 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018
Basis of Presentation
Selling, general, and administrative expenses include net foreign currency transaction gains (losses)	$ (1,608)	$ (651)	$ 701
Goodwill, Impairment Loss	$ 0
Asset Impairment Charges				$ 0

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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