Segment and Geographic Information - Financial Information for Business Segments - Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total assets	$ 1,095,257	$ 766,628
Operating Segments
Segment Reporting Information [Line Items]
Total assets	675,033	543,421
Operating Segments | Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total assets	264,452	236,755
Operating Segments | Brooks Life Sciences
Segment Reporting Information [Line Items]
Total assets	$ 410,581	$ 306,666