Revenue - Disaggregated By Timing (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 179,368	$ 142,599
Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	112,707	95,157
Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	66,661	$ 47,442
Point in time
Disaggregation of Revenue [Line Items]
Total revenue	135,083
Point in time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	111,916
Point in time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	23,167
Over time
Disaggregation of Revenue [Line Items]
Total revenue	44,285
Over time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	791
Over time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	$ 43,494