Goodwill and Intangible Assets - Goodwill Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	$ 207,154	$ 175,654
Acquisitions and adjustments	48,722	31,500
Goodwill, net of accumulated impairments, ending balance	255,876	207,154
Brooks Semiconductor Solutions Group
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	40,334	40,353
Acquisitions and adjustments	7,629	(19)
Goodwill, net of accumulated impairments, ending balance	47,963	40,334
Brooks Life Sciences
Goodwill [Roll Forward]
Goodwill, net of accumulated impairments, beginning balance	166,820	135,301
Acquisitions and adjustments	41,093	31,519
Goodwill, net of accumulated impairments, ending balance	$ 207,913	$ 166,820