Segment and Geographic Information - Financial Information for Business Segments - Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total assets	$ 1,515,999	$ 1,095,257
Reportable Segments
Segment Reporting Information [Line Items]
Total assets	1,168,795	675,033
Reportable Segments | Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total assets	259,641	264,452
Reportable Segments | Brooks Life Sciences
Segment Reporting Information [Line Items]
Total assets	$ 909,154	$ 410,581