Earnings per Share - Tabular Disclosure (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Net income
(Loss) income from continuing operations	$ (1,816)	$ (7,336)	$ 1,041	$ (4,630)
Income from discontinued operations, net of tax	2,121,690	31,084	2,162,152	54,406
Net income	2,119,874	23,748	2,163,193	49,776
Net income attributable to Brooks Automation, Inc. - basic	2,119,874	23,748	2,163,193	49,776
Net income attributable to Brooks Automation, Inc. - diluted	$ 2,119,874	$ 23,748	$ 2,163,193	$ 49,776
Weighted average common shares outstanding used in computing diluted earnings per share
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	74,958	74,265	74,823	74,142
Dilutive restricted stock units			322
Weighted average common shares outstanding used in computing diluted earnings per share (in shares)	74,958	74,265	75,145	74,142
Basic net income per share:
(Loss) income from continuing operations (in dollars per share)	$ (0.02)	$ (0.10)	$ 0.01	$ (0.06)
Income from discontinued operations, net of tax (in dollars per share)	28.31	0.42	28.90	0.73
Basic net income per share (in dollars per share)	28.28	0.32	28.91	0.67
Diluted net income per share:
(Loss) income from continuing operations (in dollars per share)	(0.02)	(0.10)	0.01	(0.06)
Income from discontinued operations, net of tax (in dollars per share)	28.31	0.42	28.77	0.73
Diluted net income per share (in dollars per share)	$ 28.28	$ 0.32	$ 28.79	$ 0.67