Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to Amtech Systems, Inc.	$ (1,420)	$ (1,499)	$ (1,475)	$ (5,513)
Weighted average shares outstanding (in shares)	13,188,000	13,169,000	13,184,000	13,161,000
Basic loss per share attributable to Amtech shareholders (USD per share)	$ (0.11)	$ (0.11)	$ (0.11)	$ (0.42)
Net loss attributable to Amtech Systems, Inc.	$ (1,420)	$ (1,499)	$ (1,475)	$ (5,513)
Weighted average shares outstanding (in shares)	13,188,000	13,169,000	13,184,000	13,161,000
Diluted shares (in shares)	13,188,000	13,169,000	13,184,000	13,161,000
Diluted loss per share attributable to Amtech shareholders (USD per share)	$ (0.11)	$ (0.11)	$ (0.11)	$ (0.42)
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,669,000	1,906,000	1,696,000	1,906,000