Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic Income (Loss) Per Share Computation
Net income (loss) attributable to Amtech Systems, Inc.	$ 3,287	$ (1,209)	$ 1,812	$ (6,722)
Weighted Average Shares Outstanding:
Common stock (in shares)	13,242	13,173	13,203	13,165
Basic income (loss) per share attributable to Amtech shareholders (USD per share)	$ 0.25	$ (0.09)	$ 0.14	$ (0.51)
Diluted Income (Loss) Per Share Computation
Net income (loss) attributable to Amtech Systems, Inc.	$ 3,287	$ (1,209)	$ 1,812	$ (6,722)
Weighted Average Shares Outstanding:
Common stock (in shares)	13,242	13,173	13,203	13,165
Common stock equivalents (in shares)	156	0	85	0
Diluted shares (in shares)	13,398	13,173	13,288	13,165
Diluted income (loss) per share attributable to Amtech shareholders (USD per share)	$ 0.25	$ (0.09)	$ 0.14	$ (0.51)
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,152	1,840	1,649	1,840