Segment and Geographic Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 897,273	$ 780,848	$ 631,560
Amortization of intangible assets	41,800	35,200	24,200
Restructuring charges	1,366	1,894	714
Operating income	78,458	46,038	31,409
Interest income	849	1,449	1,881
Interest expense	(2,944)	(22,250)	(9,520)
Loss on extinguishment of debt		(14,339)
Other expenses, net	(1,391)	(1,455)	(3,304)
Income (loss) before income taxes	74,972	9,443	20,466
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total revenue	508,736	446,669	435,018
Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Total revenue	129,759	119,020	106,146
Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Total revenue	258,778	215,159	90,396
Reportable Segments
Segment Reporting Information [Line Items]
Operating income	121,135	90,592	66,306
Reportable Segments | Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Operating income	82,950	69,961	62,511
Reportable Segments | Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Operating income	9,353	(1,835)	(9,044)
Reportable Segments | Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Operating income	28,832	22,466	12,839
Segment Reconciling Items
Segment Reporting Information [Line Items]
Acquisition accounting impact on inventory contracts acquired		184	1,896
Restructuring related charges	301	285
Segment Reconciling Items | Completed Technology
Segment Reporting Information [Line Items]
Amortization of intangible assets	11,007	10,424	4,877
Segment Reconciling Items | Acquired Intangible Assets
Segment Reporting Information [Line Items]
Amortization of intangible assets	30,766	24,737	19,339
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate (income) expenses	$ (763)	$ 7,030	$ 8,071