Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) attributable to Amtech Systems, Inc.	$ (2,965)		$ 7,298		$ (8,920)		$ 19,807
Weighted average shares outstanding (in shares)	9,479		9,576		9,468		9,446
Basic income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (0.31)		$ 0.76		$ (0.94)		$ 2.10
Common stock equivalents (1) (in shares)	0	[1]	276	[1]	0	[1]	308	[1]
Diluted shares (in shares)	9,479		9,852		9,468		9,754
Diluted income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (0.31)		$ 0.74		$ (0.94)		$ 2.03
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	892		142		892		145
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	133		0		133		0

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