Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 5,305	$ 8,086	$ (8,550)
Foreign currency translation adjustment	(1,445)	423	(199)
Comprehensive income (loss)	3,860	8,509	(8,749)
Comprehensive loss attributable to non-controlling interest	0	969	1,531
Comprehensive income (loss) attributable to Amtech Systems, Inc.	$ 3,860	$ 9,478	$ (7,218)