Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 488,602
Acquisitions and adjustments	9,900
Goodwill, net of accumulated impairments, ending balance	498,502
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	47,847
Acquisitions and adjustments	119
Goodwill, net of accumulated impairments, ending balance	47,966
Brooks Life Sciences
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	440,755
Acquisitions and adjustments	9,781
Goodwill, net of accumulated impairments, ending balance	$ 450,536