Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 255,876
Acquisitions and adjustments	234,649
Goodwill, net of accumulated impairments, ending balance	490,525
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	47,963
Acquisitions and adjustments	(167)
Goodwill, net of accumulated impairments, ending balance	47,796
Brooks Life Sciences
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	207,913
Acquisitions and adjustments	234,816
Goodwill, net of accumulated impairments, ending balance	$ 442,729