Goodwill and Intangible Assets - Reporting Units (Details) - segment	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Goodwill [Line Items]
Number of reporting units	5	5	5
Brooks Semiconductor Solutions Group
Goodwill [Line Items]
Number of reporting units	3	3	3
Brooks Life Sciences
Goodwill [Line Items]
Number of reporting units	2	2	2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration