Segment Information - Financial Information for Business Segments - Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Total assets	$ 1,503,917	$ 1,515,999
Reportable Segments
Segment Reporting Information [Line Items]
Total assets	1,237,153	1,168,795
Reportable Segments | Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total assets	289,873	259,641
Reportable Segments | Brooks Life Sciences
Segment Reporting Information [Line Items]
Total assets	$ 947,280	$ 909,154