Operations and summary of significant accounting policies (Narrative) (Details) - USD ($)	12 Months Ended			36 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2017
Basis of Presentation
Selling, general, and administrative expenses include net foreign currency transaction gains (losses)	$ (651,000)	$ 701,000	$ (1,721,000)
Goodwill, Impairment Loss	$ 0
Asset Impairment Charges				$ 0