Goodwill and Intangible Assets - Components of Goodwill by Operating Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Goodwill [Line Items]
Gross goodwill	$ 890,186	$ 848,596
Accumulated goodwill impairments	(614,958)	(614,958)
Goodwill	275,228	233,638
Brooks Semiconductor Solutions Group
Goodwill [Line Items]
Gross goodwill	655,834	655,762
Accumulated goodwill impairments	(588,944)	(588,944)
Goodwill	66,890	66,818
Brooks Life Science Systems
Goodwill [Line Items]
Gross goodwill	208,338	166,820
Goodwill	208,338	166,820
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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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