Goodwill and Intangible Assets - Components of Goodwill by Operating Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Goodwill [Line Items]
Gross goodwill	$ 1,107,484	$ 870,834
Accumulated goodwill impairments	(614,958)	(614,958)
Goodwill	492,526	255,876
Brooks Semiconductor Solutions Group
Goodwill [Line Items]
Gross goodwill	636,723	636,907
Accumulated goodwill impairments	(588,944)	(588,944)
Goodwill	47,779	47,963
Brooks Life Sciences
Goodwill [Line Items]
Gross goodwill	444,747	207,913
Goodwill	444,747	207,913
Other
Goodwill [Line Items]
Gross goodwill	26,014	26,014
Accumulated goodwill impairments	$ (26,014)	$ (26,014)

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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