Segment Information - Financial Information for Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Revenue
Products	$ 142,184	$ 122,114
Services	47,144	37,841
Total revenue	189,328	159,955
Gross profit	75,215	56,943
Segment operating income (loss)	20,840	13,161
Total assets	987,677		$ 766,628
Brooks Semiconductor Solutions Group
Revenue
Products	120,203	109,395
Services	21,683	17,221
Total revenue	141,886	126,616
Gross profit	59,453	45,468
Brooks Life Science Systems
Revenue
Products	21,981	12,719
Services	25,461	20,620
Total revenue	47,442	33,339
Gross profit	15,762	11,475
Operating Segments
Revenue
Segment operating income (loss)	26,222	17,483
Depreciation expense	2,698	2,365
Total assets	723,251		632,074
Operating Segments | Brooks Semiconductor Solutions Group
Revenue
Segment operating income (loss)	26,362	17,371
Depreciation expense	1,149	1,275
Total assets	340,367		325,408
Operating Segments | Brooks Life Science Systems
Revenue
Segment operating income (loss)	(140)	112
Depreciation expense	1,549	$ 1,090
Total assets	$ 382,884		$ 306,666