Goodwill and Intangible Assets - Components of Goodwill by Operating Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Goodwill [Line Items]
Gross goodwill	$ 1,103,560	$ 870,834	$ 822,112
Accumulated goodwill impairments	(614,958)	(614,958)	(614,958)
Goodwill	488,602	255,876	207,154
Brooks Semiconductor Solutions Group
Goodwill [Line Items]
Gross goodwill	636,791	636,907	629,278
Accumulated goodwill impairments	(588,944)	(588,944)	(588,944)
Goodwill	47,847	47,963	40,334
Brooks Life Sciences
Goodwill [Line Items]
Gross goodwill	440,755	207,913	166,820
Goodwill	440,755	207,913	166,820
Other
Goodwill [Line Items]
Gross goodwill	26,014	26,014	26,014
Accumulated goodwill impairments	$ (26,014)	$ (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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Amount of accumulated impairment loss for 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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