Segment Information and Major Customers Geographic revenue (Details) $ in Thousands			3 Months Ended								12 Months Ended
	Sep. 30, 2020 customer	Sep. 30, 2019 customer	Sep. 30, 2020 USD ($) customer	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($) customer	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2020 USD ($) customer	Sep. 30, 2019 USD ($) customer	Sep. 30, 2018 USD ($) customer
Segment Reporting Information [Line Items]
Revenue | $			$ 73,169	$ 70,338	$ 73,447	$ 62,317	$ 64,960	$ 61,166	$ 65,764	$ 62,313	$ 279,271	$ 254,203	$ 226,893
Number of customer representing over ten percent of revenue											0	0	0
Number of customer representing over ten percent of consolidated accounts receivable	1	1	1				1				1	1
Accounts Receivable
Segment Reporting Information [Line Items]
Percentage of concentration	17.20%	14.70%
United States | U.S. Export Net Sales
Segment Reporting Information [Line Items]
Percentage of concentration											25.10%	28.50%	30.10%