Segment Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total revenue	$ 220,350	$ 203,880	$ 651,077	$ 581,637
Amortization of intangible assets			31,300	26,200
Acquisition accounting impact on inventory contracts acquired				184
Restructuring charges	(29)	256	1,125	685
Operating income	19,099	16,423	44,337	35,427
Interest income	29	108	865	847
Interest expense	(810)	(8,041)	(2,265)	(21,348)
Loss on extinguishment of debt				(9,051)
Other income (expenses), net	498	(309)	(1,318)	(1,116)
Income (loss) before income taxes	18,816	8,181	41,619	4,759
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total revenue	127,052	116,040	370,786	341,624
Operating income	23,414	20,201	55,120	56,367
Brooks Life Sciences
Segment Reporting Information [Line Items]
Total revenue	93,298	87,840	280,291	240,013
Operating income	6,591	6,186	20,683	13,864
Reportable Segments
Segment Reporting Information [Line Items]
Total revenue	220,350	203,880	651,077	581,637
Segment Reconciling Items
Segment Reporting Information [Line Items]
Operating income	30,005	26,387	75,803	70,231
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate (income) expenses	545	658	(990)	7,705
Completed Technology
Segment Reporting Information [Line Items]
Amortization of intangible assets	2,779	2,863	8,194	7,661
Acquired Intangible Assets
Segment Reporting Information [Line Items]
Amortization of intangible assets	$ 7,611	$ 6,187	$ 23,137	$ 18,569