Business Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of business segments | segment			3
Net revenues	$ 32,783	$ 32,944	$ 106,394	$ 62,079
Operating income (loss)	65	(1,400)	7,831	(1,583)
Identifiable assets	171,017		$ 171,017		$ 191,623
Semiconductor | Product Concentration Risk | Sales Revenue, Product Line
Segment Reporting Information [Line Items]
Concentration risk, percentage (less than)			25.00%
Operating Segments | Solar
Segment Reporting Information [Line Items]
Net revenues	12,598	16,555	$ 61,795	27,979
Operating income (loss)	(1,903)	(1,878)	3,449	(2,901)
Identifiable assets	71,147		71,147		97,999
Operating Segments | Semiconductor
Segment Reporting Information [Line Items]
Net revenues	16,582	13,443	37,473	29,146
Operating income (loss)	2,257	1,403	5,261	3,763
Identifiable assets	59,761		59,761		57,177
Operating Segments | Polishing
Segment Reporting Information [Line Items]
Net revenues	3,603	2,946	7,126	4,954
Operating income (loss)	1,111	503	2,215	967
Identifiable assets	6,814		6,814		5,078
Non-Segment
Segment Reporting Information [Line Items]
Operating income (loss)	(1,400)	$ (1,428)	(3,094)	$ (3,412)
Identifiable assets	$ 33,295		$ 33,295		$ 31,369