Revenue from Contracts with Customers - Disaggregated By Timing (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 198,390	$ 179,368	$ 156,952	$ 377,757	$ 299,551
Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	112,877		108,413	225,584	203,570
Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	85,513	$ 66,661	$ 48,539	152,173	$ 95,981
Point in time
Disaggregation of Revenue [Line Items]
Total revenue	136,693			271,776
Point in time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	111,710			223,626
Point in time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	24,983			48,150
Over time
Disaggregation of Revenue [Line Items]
Total revenue	61,697			105,981
Over time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	1,167			1,958
Over time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	$ 60,530			$ 104,023