Segment Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 286,586	$ 220,227	$ 536,089	$ 430,727
Amortization of other intangible assets			19,700	20,900
Restructuring charges	92	578	179	1,154
Tariff adjustment	5,497		5,497
Operating income	30,505	14,572	61,434	25,238
Interest income	18	137	94	836
Interest expense	(452)	(718)	(1,008)	(1,455)
Other income (expenses), net	149	(1,399)	1,478	(1,816)
Income (loss) before income taxes	30,220	12,592	61,998	22,803
Completed Technology
Segment Reporting Information [Line Items]
Amortization of other intangible assets	2,319	2,740	4,708	5,416
Acquired Intangible Assets
Segment Reporting Information [Line Items]
Amortization of other intangible assets	7,601	7,615	14,957	15,525
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total revenue	157,051	124,923	288,409	243,734
Operating income	33,302	16,707	54,840	31,707
Brooks Life Sciences Products
Segment Reporting Information [Line Items]
Total revenue	52,355	30,993	97,866	60,717
Operating income	11,215	2,144	19,157	2,506
Brooks Life Sciences Services
Segment Reporting Information [Line Items]
Total revenue	77,180	64,311	149,814	126,276
Operating income	13,406	5,973	27,717	11,585
Reportable Segments
Segment Reporting Information [Line Items]
Total revenue	286,586	220,227	536,089	430,727
Segment Reconciling Items
Segment Reporting Information [Line Items]
Operating income	57,923	24,824	101,714	45,798
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate expense (income)	$ 11,909	$ (681)	$ 14,939	$ (1,535)