Goodwill and Intangible Assets - Components of Goodwill by Operating Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Line Items]
Gross goodwill	$ 1,116,494	$ 1,103,560	$ 870,834
Accumulated goodwill impairments	(614,958)	(614,958)	(614,958)
Goodwill	501,536	488,602	255,876
Brooks Semiconductor Solutions Group
Goodwill [Line Items]
Gross goodwill	637,303	636,791	636,907
Accumulated goodwill impairments	(588,944)	(588,944)	(588,944)
Goodwill	48,359	47,847	47,963
Brooks Life Sciences Products
Goodwill [Line Items]
Gross goodwill	103,278	101,957	104,212
Goodwill	103,278	101,957	104,212
Brooks Life Sciences Services
Goodwill [Line Items]
Gross goodwill	349,899	338,798	103,701
Goodwill	349,899	338,798	103,701
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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