Revenue from Contracts with Customers - Segment Information (Details) - segment	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Number of reportable segments	2	2	2
Number of reporting units	5	5	5
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Number of reporting units	3	3	3
Brooks Life Sciences
Segment Reporting Information [Line Items]
Number of reporting units	2	2	2