Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to Amtech Systems, Inc.	$ (3,245)	$ (5,257)	$ (3,751)	$ (794)	$ (1,682)	$ (12,101)	$ (2,092)	$ (4,194)	$ (13,047)		$ (20,069)		$ (23,031)
Weighted average shares outstanding (in shares)	9,846	9,843	9,679	9,560	9,543	9,539	9,539	9,494	9,732		9,529		9,471
Basic income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (0.33)	$ (0.53)	$ (0.39)	$ (0.08)	$ (0.18)	$ (1.27)	$ (0.22)	$ (0.44)	$ (1.34)		$ (2.11)		$ (2.43)
Common stock equivalents (in shares)									0	[1]	0	[1]		[1]
Diluted shares (in shares)	9,846	9,843	9,679	9,560	9,543	9,539	9,539	9,494	9,732		9,529		9,471
Diluted income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (0.33)	$ (0.53)	$ (0.39)	$ (0.08)	$ (0.18)	$ (1.27)	$ (0.22)	$ (0.44)	$ (1.34)		$ (2.11)		$ (2.43)
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									1,099		1,130		1,020

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