Segment Information - Financial Information for Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Revenue
Products	$ 174,113	$ 141,957	$ 476,788	$ 396,684
Services	49,367	39,760	143,280	114,321
Total revenue	223,480	181,717	620,068	511,005
Gross profit	89,221	71,572	248,665	193,039
Segment operating income (loss)	26,679	18,770	71,338	46,732
Total assets	1,091,430		1,091,430		$ 766,628
Brooks Semiconductor Solutions Group
Revenue
Products	150,675	124,681	407,903	349,710
Services	23,102	20,280	66,481	56,532
Total revenue	173,777	144,961	474,384	406,242
Gross profit	70,634	58,083	195,386	154,877
Brooks Life Sciences
Revenue
Products	23,438	17,276	68,885	46,974
Services	26,265	19,480	76,799	57,789
Total revenue	49,703	36,756	145,684	104,763
Gross profit	18,587	13,489	53,279	38,162
Operating Segments
Revenue
Segment operating income (loss)	35,708	27,322	95,449	66,097
Depreciation expense	3,063	2,326	8,933	7,055
Total assets	776,084		776,084		632,074
Operating Segments | Brooks Semiconductor Solutions Group
Revenue
Segment operating income (loss)	33,674	26,188	90,872	63,562
Depreciation expense	1,072	1,192	3,354	3,786
Total assets	361,382		361,382		325,408
Operating Segments | Brooks Life Sciences
Revenue
Segment operating income (loss)	2,034	1,134	4,577	2,535
Depreciation expense	1,991	$ 1,134	5,579	$ 3,269
Total assets	$ 414,702		$ 414,702		$ 306,666