Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 233,638
Acquisitions and adjustments	41,590
Goodwill, net of accumulated impairments, ending balance	275,228
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	66,818
Acquisitions and adjustments	72
Goodwill, net of accumulated impairments, ending balance	66,890
Brooks Life Science Systems
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	166,820
Acquisitions and adjustments	41,518
Goodwill, net of accumulated impairments, ending balance	$ 208,338