Segment and Geographic Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 780,848	$ 631,560	$ 527,499
Amortization of Intangible Assets	35,200	24,200	17,100
Operating Income (Loss)	46,038	31,409	14,319
Operating income	46,038	31,409	14,319
Amortization of acquired intangible assets	35,200	24,200	17,100
Restructuring Charges	1,894	714	3,144
Interest income	1,449	1,881	464
Interest expense	(22,250)	(9,520)	(408)
Gain on settlement of equity method investment			1,847
Loss on extinguishment of debt	(14,339)
Other expenses, net	(1,455)	(3,304)	(1,702)
Income before income taxes	9,443	20,466	14,520
Brooks Semiconductor Solutions Group
Segment Reporting Information [Line Items]
Total revenue	446,669	435,018	378,790
Operating Income (Loss)	69,961	62,511	42,741
Operating income	69,961	62,511	42,741
Restructuring Charges	600
Brooks Life Sciences
Segment Reporting Information [Line Items]
Total revenue	334,179	196,542	148,709
Operating Income (Loss)	20,631	3,795	3,217
Operating income	20,631	3,795	3,217
Restructuring Charges	1,900
Segment Reconciling Items
Segment Reporting Information [Line Items]
Amortization of Intangible Assets	24,737	19,339	13,228
Acquisition accounting impact on inventory contracts acquired	184	1,896	523
Restructuring related charges	285
Operating Income (Loss)	90,592	66,306	45,958
Operating income	90,592	66,306	45,958
Amortization of acquired intangible assets	24,737	19,339	13,228
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate expenses	7,030	8,071	10,829
Completed Technology
Segment Reporting Information [Line Items]
Amortization of Intangible Assets	10,424	4,877	3,915
Amortization of acquired intangible assets	$ 10,424	$ 4,877	$ 3,915