Goodwill and Intangible Assets - Goodwill Roll Forward (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 233,638
Acquisitions and adjustments	48,567
Goodwill, net of accumulated impairments, ending balance	282,205
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	66,818
Acquisitions and adjustments	7,395
Goodwill, net of accumulated impairments, ending balance	74,213
Brooks Life Sciences
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	166,820
Acquisitions and adjustments	41,172
Goodwill, net of accumulated impairments, ending balance	$ 207,992