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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 315,349	$ 220,350	$ 851,439	$ 651,077
Amortization of other intangible assets			30,800	31,300
Restructuring charges		(29)	179	1,125
Tariff adjustment			5,414
Operating income	50,233	19,099	111,667	44,337
Interest income	409	29	503	865
Interest expense	(477)	(810)	(1,485)	(2,265)
Other income (expenses), net	(1,625)	498	(147)	(1,318)
Income before income taxes	48,540	18,816	110,538	41,619
Completed Technology
Segment Reporting Information [Line Items]
Amortization of other intangible assets	3,352	2,779	8,060	8,194
Acquired Intangible Assets
Segment Reporting Information [Line Items]
Amortization of other intangible assets	7,733	7,611	22,690	23,137
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total revenue	186,262	127,052	474,674	370,786
Operating income	44,797	23,414	99,637	55,120
Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Total revenue	48,625	30,421	146,490	91,138
Operating income	9,138	2,482	28,295	4,988
Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Total revenue	80,462	62,877	230,275	189,153
Operating income	13,783	4,109	41,501	15,695
Operating Segments
Segment Reporting Information [Line Items]
Total revenue	315,349	220,350	851,439	651,077
Segment Reconciling Items
Segment Reporting Information [Line Items]
Operating income	67,718	30,005	169,433	75,803
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate expense (income)	$ 6,400	$ 545	$ 21,423	$ (990)