Revenue from Contracts with Customers - Disaggregated By Timing (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 210,500	$ 179,368
Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	118,811	112,707
Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	91,689	66,661
Point in time
Disaggregation of Revenue [Line Items]
Total revenue	138,108	135,083
Point in time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	116,788	111,916
Point in time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	21,320	23,167
Over time
Disaggregation of Revenue [Line Items]
Total revenue	72,392	44,285
Over time | Brooks Semiconductor Solutions Group
Disaggregation of Revenue [Line Items]
Total revenue	2,023	791
Over time | Brooks Life Sciences
Disaggregation of Revenue [Line Items]
Total revenue	$ 70,369	$ 43,494