Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2019 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 488,602
Acquisitions and adjustments	1,768
Goodwill, net of accumulated impairments, ending balance	490,370
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	47,847
Acquisitions and adjustments	35
Goodwill, net of accumulated impairments, ending balance	47,882
Brooks Life Sciences
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	440,755
Acquisitions and adjustments	1,733
Goodwill, net of accumulated impairments, ending balance	$ 442,488