Segment Information and Major Customers Geographic revenue (Details) $ in Thousands		3 Months Ended								12 Months Ended
	Sep. 30, 2015 customer	Sep. 30, 2017 USD ($) customer	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($) customer	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($) customer	Sep. 30, 2016 USD ($) customer	Sep. 30, 2015 USD ($) customer
Segment Reporting Information [Line Items]
Total revenue		$ 45,105	$ 45,739	$ 45,615	$ 45,175	$ 50,454	$ 52,130	$ 50,162	$ 50,259	$ 181,634	$ 203,005	$ 203,847
Number of customer representing over ten percent of revenue | customer										0	0	0
Number of customer representing over ten percent of consolidated accounts receivable | customer	2	0				0				0	0	2
North America, primarily United States
Segment Reporting Information [Line Items]
Total revenue										$ 117,749	$ 131,457	$ 127,592
United States | U.S. Export Net Sales
Segment Reporting Information [Line Items]
Percentage of concentration										37.10%	38.70%	39.40%
United States | Accounts Receivable | Customer 1
Segment Reporting Information [Line Items]
Percentage of concentration	10.70%
United States | Accounts Receivable | Customer 2
Segment Reporting Information [Line Items]
Percentage of concentration	11.60%
Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Total revenue										$ 39,403	$ 44,932	$ 47,523
Asia
Segment Reporting Information [Line Items]
Total revenue										19,892	20,390	22,907
Latin America
Segment Reporting Information [Line Items]
Total revenue										$ 4,590	$ 6,226	$ 5,825