CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (69,476)	$ 14,221	$ 31,522
Cumulative foreign currency translation adjustments	8,844	(9,557)	(6,296)
Unrealized gains (losses) on marketable securities, net of tax effects of $58, $(83) and $62 for fiscal years 2016, 2015 and 2014	(106)	141	(104)
Change in fair value of cash flow hedges, net of tax impact of $9 for fiscal year 2014	0	0	(14)
Actuarial losses, net of tax effects of $161, $115 and $471 for fiscal years 2016, 2015 and 2014	(322)	(605)	(503)
Pension settlement	0	232	0
Pension curtailment	852	0	0
Total other comprehensive income (loss), net of tax	9,268	(9,789)	(6,917)
Comprehensive income attributable to noncontrolling interests	0	0	(161)
Comprehensive (loss) income attributable to Brooks Automation, Inc., net of tax	$ (60,208)	$ 4,432	$ 24,444