Revenue from Contracts with Customers - Segment Information (Details) - segment	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Number of reportable segments	3	3	3
Number of reporting units	6	6	6
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Number of reporting units	3	3	3
Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Number of reporting units	1	1	1
Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Number of reporting units	2	2	2