Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Basic Income (Loss) Per Share Computation
Net income (loss) attributable to Amtech Systems, Inc.	$ 6,452		$ (53)
Weighted Average Shares Outstanding:
Common stock (in shares)	14,781		13,179
Basic income (loss) per share attributable to Amtech shareholders (USD per share)	$ 0.44		$ 0.00
Diluted Income (Loss) Per Share Computation
Net income (loss) attributable to Amtech Systems, Inc.	$ 6,452		$ (53)
Weighted Average Shares Outstanding:
Common stock (in shares)	14,781		13,179
Common stock equivalents (in shares)	517		0
Diluted shares (in shares)	15,298		13,179
Diluted income (loss) per share attributable to Amtech shareholders (USD per share)	$ 0.42		$ 0.00
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		120		1,886