Business Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of business segments | segment			3
Net revenues	$ 41,200	$ 47,760	$ 147,594	$ 109,839
Operating income (loss)	2,936	3,971	10,767	2,388
Identifiable assets	162,441		$ 162,441		$ 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	14,134	28,981	$ 75,929	56,960
Operating income (loss)	(85)	2,991	3,364	90
Identifiable assets	59,726		59,726		97,999
Operating Segments | Semiconductor
Segment Reporting Information [Line Items]
Net revenues	23,472	15,951	60,945	45,097
Operating income (loss)	3,861	2,250	9,122	6,013
Identifiable assets	60,048		60,048		57,177
Operating Segments | Polishing
Segment Reporting Information [Line Items]
Net revenues	3,594	2,828	10,720	7,782
Operating income (loss)	938	738	3,153	1,705
Identifiable assets	6,476		6,476		5,078
Non-Segment
Segment Reporting Information [Line Items]
Operating income (loss)	(1,778)	$ (2,008)	(4,872)	$ (5,420)
Identifiable assets	$ 36,191		$ 36,191		$ 31,369