Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 233,638
Acquisitions and adjustments	39,086
Goodwill, net of accumulated impairments, ending balance	272,724
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	66,818
Acquisitions and adjustments	(15)
Goodwill, net of accumulated impairments, ending balance	66,803
Brooks Life Science Systems
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	166,820
Acquisitions and adjustments	39,101
Goodwill, net of accumulated impairments, ending balance	$ 205,921