Segment and Geographic Information - Financial Information for Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Revenue
Products	$ 533,624	$ 421,783	$ 457,411
Services	159,261	138,540	95,297
Total revenue	692,885	560,323	552,708
Gross profit	267,404	198,081	189,105
Segment operating income (loss)	64,113	4,238	16,890
Depreciation expense	11,000	13,100	12,300
Total assets	766,628	685,905
Brooks Semiconductor Solutions Group
Revenue
Products	466,871	375,237	406,579
Services	77,305	76,973	78,058
Total revenue	544,176	452,210	484,637
Gross profit	212,652	159,018	171,379
Brooks Life Science Systems
Revenue
Products	66,753	46,546	50,832
Services	81,956	61,567	17,239
Total revenue	148,709	108,113	68,071
Gross profit	54,752	39,063	17,726
Operating Segments
Revenue
Segment operating income (loss)	91,411	31,476	30,115
Depreciation expense	9,746	8,284	5,607
Total assets	632,074	565,452	427,979
Operating Segments | Brooks Semiconductor Solutions Group
Revenue
Segment operating income (loss)	86,716	37,926	49,695
Depreciation expense	5,052	4,788	4,312
Total assets	325,408	317,717	317,069
Operating Segments | Brooks Life Science Systems
Revenue
Segment operating income (loss)	4,695	(6,451)	(19,580)
Depreciation expense	4,694	3,496	1,295
Total assets	$ 306,666	$ 247,735	$ 110,910