Summary of Significant Accounting Policies - Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2017	Sep. 30, 2016
Goodwill [Roll Forward]
Goodwill, gross, beginning of year	$ 12,388
Accumulated impairment losses	(1,269)
Goodwill, net, beginning of year	10,867	$ 11,119
Net foreign exchange differences	(252)
Goodwill, gross, end of quarter	12,068
Accumulated impairment losses	(1,201)
Goodwill, net, end of quarter	10,867
Solar
Goodwill [Roll Forward]
Goodwill, gross, beginning of year	6,597
Accumulated impairment losses	(1,269)
Goodwill, net, beginning of year	5,076	5,328
Net foreign exchange differences	(252)
Goodwill, gross, end of quarter	6,277
Accumulated impairment losses	(1,201)
Goodwill, net, end of quarter	5,076
Semiconductor
Goodwill [Roll Forward]
Goodwill, gross, beginning of year	5,063
Accumulated impairment losses	0
Goodwill, net, beginning of year	5,063	5,063
Net foreign exchange differences	0
Goodwill, gross, end of quarter	5,063
Accumulated impairment losses	0
Goodwill, net, end of quarter	5,063
Polishing
Goodwill [Roll Forward]
Goodwill, gross, beginning of year	728
Accumulated impairment losses	0
Goodwill, net, beginning of year	728	$ 728
Net foreign exchange differences	0
Goodwill, gross, end of quarter	728
Accumulated impairment losses	0
Goodwill, net, end of quarter	$ 728