Revenue from Contracts with Customers - Disaggregated By Timing (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 220,350	$ 203,880	$ 651,077	$ 581,637
Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	127,052	116,040	370,786	341,624
Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	93,298	87,840	280,291	240,013
Point in time
Disaggregation of Revenue [Line Items]
Total revenue	152,238	139,031	437,381	410,807
Point in time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	125,237	115,910	364,720	339,537
Point in time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	27,001	23,121	72,661	71,270
Over time
Disaggregation of Revenue [Line Items]
Total revenue	68,112	64,849	213,696	170,830
Over time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	1,815	130	6,066	2,087
Over time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	$ 66,297	$ 64,719	$ 207,630	$ 168,743