Segment Information - Financial Information for Business Segments - Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total assets	$ 1,664,096	$ 1,559,125
Reportable Segments
Segment Reporting Information [Line Items]
Total assets	1,319,896	1,248,452
Reportable Segments | Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total assets	322,423	296,289
Reportable Segments | Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Total assets	230,732	214,196
Reportable Segments | Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Total assets	$ 766,741	$ 737,967