Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (5,162)	$ 5,305	$ 8,086
Foreign currency translation adjustment	(1,746)	(1,445)	423
Reclassification adjustment for net foreign currency translation losses included in net income	487
Comprehensive (loss) income	(6,421)	3,860	8,509
Comprehensive loss attributable to non-controlling interest			969
Comprehensive (loss) income attributable to Amtech Systems, Inc.	$ (6,421)	$ 3,860	$ 9,478