Segment and Geographic Information - Financial Information for Business Segments - Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Total assets	$ 1,559,125	$ 1,515,999
Reportable Segments
Segment Reporting Information [Line Items]
Total assets	1,248,452	1,168,795
Reportable Segments | Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total assets	296,289	259,641
Reportable Segments | Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Total assets	214,196	206,456
Reportable Segments | Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Total assets	$ 737,967	$ 702,698