Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 488,602
Acquisitions and adjustments	11,460
Goodwill, net of accumulated impairments, ending balance	500,062
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	47,847
Acquisitions and adjustments	316
Goodwill, net of accumulated impairments, ending balance	48,163
Brooks Life Sciences
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	440,755
Acquisitions and adjustments	11,144
Goodwill, net of accumulated impairments, ending balance	$ 451,899