Summary of Significant Accounting Policies - Goodwill (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Sep. 30, 2016
Goodwill [Line Items]
Goodwill, gross		$ 12,517	$ 12,388
Accumulated impairment losses		(1,297)	(1,269)
Goodwill, net	$ 11,119	11,220	11,119
Goodwill [Roll Forward]
Goodwill, beginning of period	11,119
Net foreign exchange differences	101
Goodwill, end of period	11,220
Solar
Goodwill [Line Items]
Goodwill, gross		6,726	6,597
Accumulated impairment losses		(1,297)	(1,269)
Goodwill, net	5,328	5,429	5,328
Goodwill [Roll Forward]
Goodwill, beginning of period	5,328
Net foreign exchange differences	101
Goodwill, end of period	5,429
Semiconductor
Goodwill [Line Items]
Goodwill, gross		5,063	5,063
Accumulated impairment losses		0	0
Goodwill, net	5,063	5,063	5,063
Goodwill [Roll Forward]
Goodwill, beginning of period	5,063
Net foreign exchange differences	0
Goodwill, end of period	5,063
Polishing
Goodwill [Line Items]
Goodwill, gross		728	728
Accumulated impairment losses		0	0
Goodwill, net	728	$ 728	$ 728
Goodwill [Roll Forward]
Goodwill, beginning of period	728
Net foreign exchange differences	0
Goodwill, end of period	$ 728