Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Goodwill [Line Items]
Goodwill	$ 13,469	$ 13,469	$ 12,753
Accumulated impairment losses	(6,836)	(6,836)	(1,348)
Goodwill [Roll Forward]
Carrying value		11,405
Impairment of goodwill		(5,663)
Net exchange differences		891
Carrying value	6,633	6,633
Solar
Goodwill [Line Items]
Goodwill	6,836	6,836	6,962
Accumulated impairment losses	(6,836)	(6,836)	(1,348)
Goodwill [Roll Forward]
Carrying value		5,614
Impairment of goodwill	(5,700)	(5,663)
Net exchange differences		49
Carrying value	0	0
Semiconductor
Goodwill [Line Items]
Goodwill	5,905	5,905	5,063
Accumulated impairment losses	0	0	0
Goodwill [Roll Forward]
Carrying value		5,063
Impairment of goodwill		0
Net exchange differences		842
Carrying value	5,905	5,905
Polishing
Goodwill [Line Items]
Goodwill	728	728	728
Accumulated impairment losses	0	0	$ 0
Goodwill [Roll Forward]
Carrying value		728
Impairment of goodwill		0
Net exchange differences		0
Carrying value	$ 728	$ 728

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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