Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2016	Apr. 21, 2016
Document and Entity Information [Abstract]
Trading Symbol	BRKS
Entity Registrant Name	BROOKS AUTOMATION INC
Entity Central Index Key	0000933974
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		68,616,306