Earnings per Share - Reconciliation of Weighted Average Common Shares Outstanding for Purposes of Calculating Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net income attributable to Brooks Automation, Inc.	$ (2,215)	$ 136,789	$ 130,385
Weighted average common shares outstanding used in computing basic earnings per share	65,912	65,128	64,549
Dilutive common stock options and restricted stock awards	0	594	454
Weighted average common shares outstanding for purposes of computing diluted earnings per share	65,912	65,722	65,003
Basic net income per share attributable to Brooks Automation, Inc. common stockholders	$ (0.03)	$ 2.10	$ 2.02
Diluted net income per share attributable to Brooks Automation, Inc. common stockholders	$ (0.03)	$ 2.08	$ 2.01