Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) attributable to Amtech Systems, Inc.	$ (14,111)	$ (2,965)	$ (5,079)	$ (876)	$ 3,075	$ 7,298	$ 7,517	$ 4,992	$ (23,031)		$ 22,882		$ 9,563
Weighted average shares outstanding (in shares)	9,482,000	9,479,000	9,479,000	9,446,000	9,581,000	9,576,000	9,487,000	9,278,000	9,471,000		9,480,000		9,022,000
Basic income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (1.49)	$ (0.31)	$ (0.54)	$ (0.09)	$ 0.32	$ 0.76	$ 0.79	$ 0.54	$ (2.43)		$ 2.41		$ 1.06
Common stock equivalents (1) (in shares)									0	[1]	284,000	[1]	215,000	[1]
Diluted shares (in shares)	9,482,000	9,479,000	9,479,000	9,446,000	9,778,000	9,852,000	9,781,000	9,609,000	9,471,000		9,764,000		9,237,000
Diluted income (loss) per share attributable to Amtech shareholders (dollars per share)	$ (1.49)	$ (0.31)	$ (0.54)	$ (0.09)	$ 0.31	$ 0.74	$ 0.77	$ 0.52	$ (2.43)		$ 2.34		$ 1.04
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									1,020,000		145,000		229,000

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