Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to Amtech Systems, Inc.	$ (1,682)	$ (12,101)	$ (2,092)	$ (4,194)	$ (14,111)	$ (2,965)	$ (5,079)	$ (876)	$ (20,069)		$ (23,031)		$ 22,882
Weighted average shares outstanding (in shares)	9,543	9,539	9,539	9,494	9,482	9,479	9,479	9,446	9,529		9,471		9,480
Basic income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (0.18)	$ (1.27)	$ (0.22)	$ (0.44)	$ (1.49)	$ (0.31)	$ (0.54)	$ (0.09)	$ (2.11)		$ (2.43)		$ 2.41
Common stock equivalents (in shares)									0	[1]	0	[1]	284	[1]
Diluted shares (in shares)	9,543	9,539	9,539	9,494	9,482	9,479	9,479	9,446	9,529		9,471		9,764
Diluted income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (0.18)	$ (1.27)	$ (0.22)	$ (0.44)	$ (1.49)	$ (0.31)	$ (0.54)	$ (0.09)	$ (2.11)		$ (2.43)		$ 2.34
Stock Options and Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									1,130		1,020		145

[1] (1) The number of common stock equivalents is calculated using the treasury stock method and the average market price during the period.