CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total Brooks Automation, Inc. Stockholders’ Equity	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock	Noncontrolling Interests in Subsidiaries	Total
Beginning Balance at Sep. 30, 2015	$ 632,045	$ 811	$ 1,846,357	$ 5,898	$ (1,020,065)	$ (200,956)		$ 632,045
Beginning Balance (in shares) at Sep. 30, 2015		81,093,052
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock option, restricted stock and purchase plans, net	(2,381)	$ 10	(2,391)					(2,381)
Shares issued under stock option, restricted stock and purchase plans, net (in shares)		1,127,218
Stock-based compensation	11,737		11,737					11,737
Common stock dividend declared, at $0.40, $0.40 and $0.40 per share for fiscal years 2017, 2016 and 2015, respectively	(27,503)				(27,503)			(27,503)
Comprehensive income (loss):
Net income (loss)	(69,476)				(69,476)			(69,476)
Foreign currency translation adjustments	8,844			8,844				8,844
Changes in unrealized gains (losses) on marketable securities, net of tax effects of $0, $0, and $58 for fiscal years 2018, 2017 and 2016, respectively	(106)			(106)				(106)
Actuarial gains (losses), net of tax effects of ($49), ($74) and $161 for fiscal years 2018, 2017 and 2016	(322)			(322)				(322)
Pension curtailment (settlement)	852			852				852
Ending Balance at Sep. 30, 2016	553,690	$ 821	1,855,703	15,166	(1,117,044)	(200,956)		553,690
Ending Balance (in shares) at Sep. 30, 2016		82,220,270
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock option, restricted stock and purchase plans, net	1,949	$ 12	1,937					1,949
Shares issued under stock option, restricted stock and purchase plans, net (in shares)		1,074,578
Stock-based compensation	17,278		17,278					17,278
Common stock dividend declared, at $0.40, $0.40 and $0.40 per share for fiscal years 2017, 2016 and 2015, respectively	(27,932)				(27,932)			(27,932)
Comprehensive income (loss):
Net income (loss)	62,612				62,612			62,612
Foreign currency translation adjustments	(221)			(221)				(221)
Changes in unrealized gains (losses) on marketable securities, net of tax effects of $0, $0, and $58 for fiscal years 2018, 2017 and 2016, respectively	2			2				2
Actuarial gains (losses), net of tax effects of ($49), ($74) and $161 for fiscal years 2018, 2017 and 2016	525			525				525
Pension curtailment (settlement)	(259)			(259)				(259)
Ending Balance at Sep. 30, 2017	607,644	$ 833	1,874,918	15,213	(1,082,364)	(200,956)		$ 607,644
Ending Balance (in shares) at Sep. 30, 2017		83,294,848						69,832,979
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock option, restricted stock and purchase plans, net	2,826	$ 8	2,818					$ 2,826
Shares issued under stock option, restricted stock and purchase plans, net (in shares)		869,282
Stock-based compensation	19,822		19,822					19,822
Common stock dividend declared, at $0.40, $0.40 and $0.40 per share for fiscal years 2017, 2016 and 2015, respectively	(28,285)				(28,285)			(28,285)
Acquisition of noncontrolling interest	876		876				$ 111	987
Comprehensive income (loss):
Net income (loss)	116,575				116,575		$ (111)	116,464
Foreign currency translation adjustments	(1,651)			(1,651)				(1,651)
Changes in unrealized gains (losses) on marketable securities, net of tax effects of $0, $0, and $58 for fiscal years 2018, 2017 and 2016, respectively	(111)			(111)				(111)
Actuarial gains (losses), net of tax effects of ($49), ($74) and $161 for fiscal years 2018, 2017 and 2016	136			136				136
Ending Balance at Sep. 30, 2018	$ 717,832	$ 841	$ 1,898,434	$ 13,587	$ (994,074)	$ (200,956)		$ 717,832
Ending Balance (in shares) at Sep. 30, 2018		84,164,130						70,702,261